Besides　the　design　and　synthesis　of　nonfullerene　acceptors,　the　selection　of　polymer　donors　is　also　critical　in　determining　the　photovoltaic　performance　of　nonfullerene　organic　solar　cells　(OSCs).　However,　the　selection　criteria　of　polymer　donors　for　nonfullerene　OSCs　has　been　rarely　investigated.　In　this　work,　a　novel　nonfullerene　acceptor　(MDB)　with　spa-hybridized-carbon-free　ladder-type　skeleton　was　developed　and　used　as　a　model　compound　to　study　the　effects　of　miscibility　and　molecular　ordering　in　determining　the　performance　of　MDB-based　solar　cells.　In　order　to　achieve　matched　energy　levels　and　complementary　absorption,　three　wide-bandgap　polymers　(PM6,　T71,　and　P3HT)　with　different　chemical　structures　were　selected　to　blend　with　MDB　for　OSCs.　The　donor:acceptor　miscibilities　of　the　three　blends　were　estimated　by　contact　angle　measurements,　while　their　crystallinity　and　phase　separation　were　investigated　by　grazing　incidence　wide-angle　X-ray　scattering　characterization　and　atomic　force　microscopy　measurement,　respectively.　The　interfacial　tension　values　between　MDI3　and　PM6,　MDB　and　J71,　as　well　as　MDB　and　P3HT　were　determined　as　0.49,　0.16,　and　2.00　mN.m(-1),　in　that　order.　Owing　to　the　proper　miscibility　between　MDB　and　PM6,　the　resulting　blend　film　exhibits　suitable　phase　separation,　＂face-on＂　molecular　orientation　as　well　as　compact　molecular　pi-pi　stacking,　which　promotes　carrier　transport　and　suppresses　bimolecular　recombination.　As　a　result,　the　best-performance　OSC　based　on　PM6:MDB　delivered　an　outstanding　PCE　of　13.26%.　In　contrast,　J71:MDB-based　devices　exhibited　a　lower　PCE　of　8.16%,　due　to　the　excessively　high　miscibility　of　J71　and　MDB.　As　for　P3HT:MDB-based　devices,　the　poor　miscibility　between　P3HT　and　MDB　provides　the　driving　force　for　the　formation　of　large　phase　separation,　which　leads　to　an　extremely　low　PCE　of　0.45%.　This　work　demonstrates　that　suitable　miscibility　is　one　of　the　key　factors　to　achieve　high-performance　OSCs,　which　is　an　important　guideline　for　the　design　and　selection　of　next-generation　photovoltaic　materials.