Abstract: The sweet cherry Lapins and Rainier were S1S4 genotype，self-pollination rate of Lapinswas 31.3%，performed self-compatibility and that of Rainier was 0，showed self-incompatibility. In the reciprocal cross experiment，it showed compatible when Lapins was the male parent，however，it showed incompatible if using Rainier as male parent. This result suggested that the reason of the Lapins self-compatibility might be caused by pollen side mutation；The pollen germination rate of Lapins was 58.08% and that of Rainier was 57.82%. The S genotypes offspring of self-pollination and cross-pollination were identified by Rainier and the results showed that S4 genotype can be detected in all generations，but S1 genotype was in part of the offspring，this further proved that Lapins pollen can germinate normal，and the self-compatibility may be caused by a mutated gene on S4 genotype pollen side. Previous studies had found that Lapins pollen SFB4 has 4 nucleotide deletion in 911 bp，and this SFB4′ gene linked style S4-RNase closely in our experiment，the linkage rate was 100%；The self-fruit rate ranged from 23.3% to 61.4% in the offsprings contained SFB4′，suggest that Lapins self-compatible may be determined by SFB4′；RT-PCR and sequencing displayed that Lapins SFB4′ and Rainier SFB4 can transcription normally，but 4 bp DNA deletion should cause a truncated protein in C terminal，and SDS-PAGE showed that the SFB4-GST fusion protein was a bit bigger than the SFB4′-GST protein. The results above showed that：The self-compatible of Lapins may be caused by the pollen side SFB4′ mutation，amino acid deletion may lead SFB4′ loss the ability to recognize S-RNase.

Key words: sweet cherry, self-incompatibility, pollen, SFB4′, amino acid deletion