A modified mRNA differential display method has been applied to studying differential expression of protein kinase genes in oocytes between natural gynogenetic silver crucian carp and amphimictic crucian carp. Total RNA was reverse transcribed using downstream 3′ primers T12MA, T12MG and T12MC respectively. Then the reverse transcription products were amplified using upstream 5′ kinase-specific primer designed according to protein kinase conserved sequence. The PCR products had different patterns and numbers of cDNA bands on polyacrylamide gel. Totalty 21 cDNAs fragments were recovered and cloned. Two of them were confirmed to be particularly expressed in oocytes of amphimictic crucian carp, and another was specific for gynogenetic silver crucian carp.