The HA and NA glycosylation of an influenza strain can affect its host specificity, virulence and infectivity either directly, by changing the biologic properties of HA and NA, or indirectly, by attenuating receptor binding, masking antigenic regions of the protein, impeding the activation of the protein precursor HA0 via its cleavage into the disulfide-linked subunits HA1 and HA2, regulating catalytic activity or preventing proteolytic cleavage of the stalk of NA. In our previous work, by using a series of bioinformatics tools, we found that increase of glycosite numbers was mainly occurred in the early evolutionary stages of human seasonal influenza A/H1N1 viruses, while glycosite migration became the dominating mode in the later evolutionary stages. Importantly, we elucidated that the positional conversion of glycosites might be a more effective mode of glycosite alteration for the evolution of influenza A/H1N1 viruses, by analyzing the speed of a new mutant strain overtakes its original one. In this study, we provided more bioinformatics and statistic data to further predict the significant biological functions of glycosite migration in the host adaption of human influenza H1N1 viruses. Several possible biological functions of glycosite migration in human H1N1 viruses were summarized in this paper. These predictions still needs to be supported by experimental data,11-hydroxy-sugiol the information here can provide some constructive suggestions for the research related to the functions of protein glycosylation in influenza viruses. This may be one of the reasons that glycosite 179 was replaced by glycosite 177 in 1951. The variability analysis on antigenic sites of HA also showed that the amino acid variations decreased at the antigenic site Sb but increased at the antigenic site Ca2 after 1951, which supported the modeling results to a certain degree. Glycosite 144 appeared on the top of the HA head in human influenza H1N1 viruses in 1940 and was replaced by glycosite 172 in 1947. Then, the acquisition of glycosite 142 in 1986 may have rendered glycosite 172 unnecessary because glycosite 172 ultimately disappeared in 1987. The glycans at glycosites 142 may shield the antigenic site Sa more effectively because it is located at the center Sa,aurantiamide-acetate while glycosites 172 is at the edge of the antigenic site and glycosite 144 is adjacent to Sa. That should also be one of the important reasons why the amino acid variations of HA at Sa site after 1940 continuously decreased till 1985. The glycosite migrations between different regions may collaborate with each other. For example, the glycans at glycosite 144 may be better in shielding antigenic site Sb than glycans at glycosites 172 and 142, but since glycans at glycosite 177 on the adjacent subunit can shield this antigenic site well, the glycosite 142 become more preponderant than glycosite 144 as it is better in protecting antigenic Sa site. In fact, these glycosite migrations may result in totally different antigenic activity for influenza H1N1 viruses. Previous reports had shown that there was no crossprotection existed between H1 vaccines produced before and after 1986. Our analysis revealed that this might be due to the glycosites migrations from site 172 to site 142 and/or from sites 286 and 104 to site 71, because all three vaccine strains before 1986 had the same glycosite patterns on HA, but glycosites 172 and 286 had been replaced by glycosites 142 and 71 since 1986, respectively. Besides, glycosite 365 was also replaced by glycosite 434 in 1986 which might also have some effects on the cross-protection of vaccines. In this study, homology modeling and in silico protein glycosylation of representative HA and NA proteins as well as amino acid variability analysis at antigenic sites were employed for predicting biological functions of glycosite migrations in the host adaptation of human seasonal influenza H1N1 viruses.