Abstract: The mitochondrial genetic patterns of bivalve mollusc are different from the traditional maternal inheritance. The mitochondria of bivalve molluscs have two kinds of mtDNA of M type and F type, which are called doubly uniparental inheritance (DUI). In order to explore the mechanism of DUI, the full-length cDNA of M and F-type COⅡ genes in Hyriopsis cumingii was obtained by RACE. qRT-PCR was used to detect the expression of M and F-type COⅡ genes in different tissues and stages. The results are as follows: 1.The full-length cDNA sequences of M-type COⅡ gene and F-type COⅡ gene were 1244 bp and 808 bp respectively, and the 3′ end of M-type COⅡ gene had a prolonged sequence of 546 bp. The transmembrane structure prediction showed that there were four transmembrane structures in the C-terminus extension region of the M-type COⅡ gene, suggesting that this extension sequence has certain function. 2. M-type COⅡ gene and F-type COⅡ gene were all expressed in the early juvenile (embryonic to 5-month-old) of H.cumingii, and the expression level of F-type COⅡ gene was significantly higher than that of M-type COⅡ gene. 3. In the tissues of six-month-old mussels, the expression of M-type COⅡ gene was the highest in gonads, and the expression of F-type COⅡ gene was still at a high level in the same tissues. 4. In the one-year-old female tissues, M and F-type COⅡ genes can be detected in all tissues. In male tissues, the F-type COⅡ gene was detected in each tissues, but M-type COⅡ gene was only expressed in gonads. 5. In the two-year-old female tissues, F and M type both expressed in each tissue, but the expression of M-type COⅡ gene is very low. In the two-year-old male tissues, the F-type COII gene was detectable in addition to the gonad, and the M-type COⅡ gene was detected only in the gonad. In the two-year-old male tissues, the F-type COⅡ gene was detectable except for the gonad, and the M-type COⅡ gene was detected only in the gonad. These results suggested that M-type mtDNA is selectively degraded or aggregated in tissues during male and female development of H. cumingii.