Abstract: In the experiments the cytoplasmic male sterility lines from Honglian type and Yiebai type rice were used. Chloroplasts were purified by discontinous sugar density gradiet centrifugation, and mtDNAs were isolated with saturated phenol-chloroferm-iso-Amyl alcohol method. In comparative study on those mtDNAs, it is indicated that there were some small cycle mtDNAs named m₂, m₃ and these small cyele mtDNAs were different between two cytoplasm types based on agarose gel electrophores and electron microscope observation. No difference was founded in the great-molecular mtDNAs named m₃ between sterile and maintainer lines. The experiments also dealt with biochemistic character of mtDNA m₁.