Eriocheir sinensis is an important economic crab in China; it has a typical migratory habit, including an annual reproductive migration from November to May and for mating and spawning at the confluence of salty and fresh water at the mouth of the Yangtze River. When the broodstock crab spawns, the fertilized egg will commence a new life cycle. At this time, temperature is one of the key environmental factors regulating the development of the embryo, which is particularly sensitive to ambient temperature during its development, and even small temperature differences may cause stagnation of embryonic development. Therefore, it is important to investigate the effect of temperature on embryonic development of E. sinensis. In order to explore the molecular mechanism of temperature-regulated embryonic development in E. sinensis, three experimental groups were set up, namely, constant temperature of 9 ℃, constant temperature of 15 ℃, and gradually increasing temperature from 9 ℃ to 15 ℃. We utilized transcriptomics to screen genes associated with embryonic development and to identify the signaling pathways involved in the temperature-regulated embryonic development. The results showed that temperature significantly affected embryonic development process and effective cumulative temperature. At a constant temperature of 9 ℃, the embryos were stagnant at the egg cleavage stage, and their effective cumulative temperature was 1961.95 h·℃. In the experimental group, with a gradual temperature increase from 9 ℃ to 15 ℃, the embryos were able to develop to the prothallus larval stage, and embryo development time and effective cumulative temperature were reduced by 144 h and 1303.77 h·℃, respectively, compared with that under a constant temperature of 15 ℃. Temperature changes significantly regulated the expression patterns of genes related to embryo development. A total of 4767 differentially expressed genes were identified under a temperature increase from 9 ℃ to 15 ℃, including 1800 up-regulated genes and 2967 down-regulated genes. The gap gene (LOC126998238) related to embryonic development was significantly down-regulated, and the functional pathway was mainly enriched in endoplasmic reticulum protein targeting. At a constant temperature of 15 ℃, a total of 2061 differentially expressed genes were identified, including 1326 up-regulated genes and 735 down-regulated genes. Further analysis revealed that the maternal effect gene (LOC126984051) was significantly up-regulated in embryos, and the functional pathways were mainly enriched in small molecule metabolism. The results showed that embryo development accelerated with increasing temperature within a certain range and that variable temperature accelerated embryo development more than constant temperature. Variable temperature significantly increased the expression of genes related to embryonic development and embryonic energy metabolism, and it accelerated embryonic development. The results of this study can provide a theoretical reference for the interpretation of the regulatory mechanism of temperature on the embryonic development of E. sinensis.