OTFT　devices　were　fabricated　through　inkjet　printing　active　layer　on　SiO2　dielectric.　To　improve　the　device　performance,　SiO2　layer　was　modified　with　octadecyltrichlorosilane　(OTS)　or　a　thin　layer　of　Al2O3　(1　nm)　by　atomic　layer　deposition.　The　surface　morphology,　contact　angle　of　PDVT-8　solution　on　the　dielectric　layer,　and　the　crystalline　of　the　inkjet　printing　active　layers　were　examined.　The　surface　morphology　of　the　modified　dielectric　layer　is　slightly　various　with　SiO2　layer,　while　the　contact　angle　and　crystalline　of　the　inkjet　printing　active　layer　change　significantly.　For　OTS-treated　dielectric　layer　and　ALD　Al2O3-treated　dielectric　layer,　the　mobility　increases　4　times　and　9　times,　while　the　on/off　current　ratio　increases　1　order　of　magnitude　and　4　orders　of　magnitude,　respectively,　The　maximum　value　of　mobility　and　the　on/off　current　ratio　are　0.35　cm2/(V·s)　and　6.0×106.　©　2017,　Science　Press.　All　right　reserved.