To make identification between Paragonimus menglaensis and Paragonimus proliferus.Crabs were collected from same area where P. proliferus and P. menglaensi were reported, metacercariae and excysted metacercariae were separated. Adult worms were collected from experimental infection and identified.The metacercaria is large, with an average size of (1.23 +/- 0.087) mm x (1.10 +/- 0.073) mm, covered with a thin and fragile cyst wall; the size of excysted metacercariae is (2.01 +/- 0.71) mm x (0.62 +/- 0.12) mm, with irregular bough-like wrinkles excretory bladder resembling in front of ventral sucker, two pointed and slim distal ends of gut locate at 1/6 of the body from the tail end; the adult worm has large uterine mass, with an average length of 1/4.2 of the whole body. The natural definitive host for P. proliferus is not monkeys, dogs, and cats, but rats. The metacercaria of the reported P. menglaensis has been mixed up with that of P. microrchis from the same crab, excysted metacercaria has been same to that of P. proliferus, and an immature worm has been mistakenly identified as its adult worm.P. proliferu is a valid independent species, while P. menglaensis is a mis-identified, invalid one.