In order to establish a quick and accurate determination method of whether the oocyte of Chinese mitten crab (Eriocheir sinensis) is mature or not, a series of experiments were carried out referred to the clearing solution’s ingredients of oocyte in zebrafish. Finally, we found that the mixture of 60 percent of ethanol, 1 percent of acetic acid and 30 percent of formaldehyde was useful for the oocyte of Chinese mitten crab. White spots could be observed in immature oocytes after treated with the mixture, while in mature oocytes, no white spot could be seen. And it is consistent with the result of optical microscopy and H.E staining. Obviously, the mixture of 60 percent of ethanol, 1 percent of acetic acid and 30 percent of formaldehyde could be used to determine whether the oocyte of E. sinensis is mature.