To improve the hatching effect of red claw crayfish embryos in vitro and provide basic water quality data for large-scale incubation, in this study, the ZISS incubator was used to explore the effect of pH on the in vitro incubation performances of red claw crayfish embryos, such as hatch time (to freely moving juveniles stage 3), hatching amount (the number of juvenile shrimps reaching stage 3), hatching rate and survival rate etc., in the wish to find out the optimal pH level. At water temperature of 28±0.5℃, 7 pairs of appendage embryos were stripped with a comb, soaked in 3 000 mg/L formaldehyde for 15 min, then incubated in a ZISS incubator respectively at pH of 6.8, 7.7, 8.4, 8.9 and 9.4 adjusted by 30%~40% HCI and NaOH, for a 25-day experiment. The results showed that there was no significant difference in hatching rate among all the groups (P > 0.05). However, the red claw crayfish exposed to pH 7.7 and pH 8.4 had significantly higher survival rates than those in the other three groups (P<0.05), with 0% survival rate in pH 6.8 group, and without significant difference from that in pH 9.4 group (P>0.05). There was significantly lower survival rate in the two groups than that in the other three groups (P<0.05), with downward trend of survival rates between pH 7.7 and 9.4 groups. Changes in pH value during incubation did not led to a large number of embryo death, with the death peak of embryo in all pH groups on the 5th day, and the longer incubation period of the embryos in pH 6.8 group. In the pH 7.7 and 9.4 groups, a large number of death juveniles were found, while not found in the three middle pH value groups. Red claw crayfish juveniles were observed in 19d and 25d. The results showed that the hatching rate of in vitro embryos of red crayfish was not affected by pH changes within a pH range of 6.8 ~ 9.4. However, low pH will prolong the incubation time of embryos and make the young shrimps unable to survive after hatching, leading to  the phenomenon of acidosis and resulting in physiological hypoxia and final death of embryos and young crayfish.
While when pH is too high, the decrease of calcium ion content and CO32 - poisoning may be the reasons for the first mass death of young shrimps. According to the experiment,, the optimal pH for in vitro embryo hatching of red crayfish is 8.1. This result provides a concrete optimal pH value for the hatching processes, which will be helpful to improve the hatching rate and survival rate, and play a guiding role in future practical production.