In　general,　cross-link　is　applied　into　conjugated　polymers　for　improving　stability　of　organic　solar　cells,　but　its　effect　on　the　photovoltaic　performance　received　little　attention.　Particularly,　cross-linked　conjugated　polymers　with　poor　solubility　show　strong　aggregation　in　bulk-heterojunction　thin　films,　resulting　in　low　charge　generation　efficiencies　and　hence　poor　performance　in　solar　cells.　Herein,　we　were　able　to　develop　a　series　of　cross-linked　conjugated　polymers　as　electron　donor　for　application　in　organic　solar　cells　with　a　non-fullerene　acceptor　IT-4F,　in　which　the　photovoltaic　performance　and　morphological　stability　in　a　nitrogen　environment　could　be　significantly　improved.　The　polymers　contain　an　electron-deficient　thieno[3,4-c]pyrrole-4,6-dione　(TPD)　unit　alternated　with　two-dimensional　benzodithiophene,　in　which　a　four　brominated-TPD　monomer　was　applied　into　polymerization　to　obtain　cross-linked　polymers.　All　these　cross-linked　polymers　perform　identical　absorption　spectra,　energy　levels,　and　hole　mobilities　with　the　non-cross-linked　polymer,　but　their　photovoltaic　performance　was　different.　The　cross-linked　polymer　containing　3%　cross-linker　as　electron　donor　realized　a　high　power　conversion　efficiency　of　12.18%　in　non-fullerene　organic　solar　cells,　while　the　polymer　donor　without　cross-linker　only　provided　a　low　PCE　of　7.56%.　The　greatly　enhanced　performance　in　cross-linked　polymer　solar　cells　was　due　to　optimized　nanophase　separation　with　crystalline　and　small　domain　in　blended　thin　films,　resulting　in　efficient　charge　generation.　Our　results　demonstrate　that　by　rationally　designing　cross-linked　conjugated　polymers,　it　is　possible　to　simultaneously　obtain　high　performance　and　morphological　stability　in　a　nitrogen　environment　in　organic　solar　cells,　enabling　their　great　potential　application　in　large-area　devices.