Objective To assess the value of ultrasonography in the diagnosis of ovarian pregnancy (OP). Methods The characteristics of transvaginal ultrasound and color Doppler flow imaging of 38 cases of OP were reviewed, whose diagnoses were confirmed by operations and pathologic findings. Results Twenty eight cases(~73.7 %) were correctly diagnosed by ultrasound, nine cases(~23.7 %) were misdiagnosed either as lutein cysts or as tubal pregnancy, one case(~2.6 %) was missed by ultrasound examination. According to ultrasound findings, 24 cases(~63.2 %) were diagnosed as type of gestational sac, 14(~36.8 %) cases as type of complex mass. Conclusions Ultrasonography plays an important role in diagnosing OP, especially in earlier OP of the gestational sac type.