Background:　School　closure　is　a　common　mitigation　strategy　during　severe　influenza　epidemics　and　pandemics.　However,　the　effectiveness　of　this　strategy　remains　controversial.　In　this　study,　we　aimed　to　explore　the　effectiveness　of　school　closure　on　seasonal　influenza　epidemics　in　provincial-level　administrative　divisions　(PLADs)　with　varying　urbanization　rates　in　China.　Methods:　This　study　analyzed　influenza　surveillance　data　between　2010　and　2019　provided　by　the　Chinese　National　Influenza　Center.　Taking　into　consideration　the　climate,　this　study　included　a　region　with　3　adjacent　PLADs　in　Northern　China　and　another　region　with　4　adjacent　PLADs　in　Southern　China.　The　effect　of　school　closure　on　influenza　transmission　was　evaluated　by　the　reduction　of　the　effective　reproductive　number　of　seasonal　influenza　during　school　winter　breaks　compared　with　that　before　school　winter　breaks.　An　age-structured　Susceptible-Infected-Recovered-Susceptible　(SIRS)　model　was　built　to　model　influenza　transmission　in　different　levels　of　urbanization.　Parameters　were　determined　using　the　surveillance　data　via　robust　Bayesian　method.　Results:　Between　2010　and　2019,　in　the　less　urbanized　provinces:　Hebei,　Zhejiang,　Jiangsu　and　Anhui,　during　school　winter　breaks,　the　effective　reproductive　number　of　seasonal　influenza　epidemics　reduced　14.6%　[95%　confidential　interval　(CI):　6.2-22.9%],　9.6%　(95%　CI:　2.5-16.6%),　7.3%　(95%　CI:　0.1-14.4%)　and　8.2%　(95%　CI:　1.1-15.3%)　respectively.　However,　in　the　highly　urbanized　cities:　Beijing,　Tianjin　and　Shanghai,　it　reduced　only　5.2%　(95%　CI:　-0.7-11.2%),　4.1%　(95%　CI:　-0.9-9.1%)　and　3.9%　(95%　CI:　-1.6-9.4%)　respectively.　In　China,　urbanization　is　associated　with　decreased　proportion　of　children　and　increased　social　contact.　According　to　the　SIRS　model,　both　factors　could　reduce　the　impact　of　school　closure　on　seasonal　influenza　epidemics,　and　the　proportion　of　children　in　the　population　is　thought　to　be　the　dominant　influencing　factor.　Conclusions:　Effectiveness　of　school　closure　on　the　epidemics　varies　with　the　age　structure　in　the　population　and　social　contact　patterns.　School　closure　should　be　recommended　in　the　low　urbanized　regions　in　China　in　the　influenza　seasons.