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To discuss the stragedy of the overwintering egg in Oxya chinensis Thunberg, this research used four populations collected from Tieling (42.5°N), Jinan (36.8°N), Changsha (28.3°N), Danzhou (19.5°N). Rearch the characters of embryonic development, the stage of egg’s diapause, the geographic variation of egg’s cold hardiness, the developmental zero and the effective accumulated temperature. The main results are as followed:(1) According to the different embryonic morphology, the embryonic development was devided into 11 stages. Detect the regular change of water content and fresh weight of every population in the process of embrynic development. In 25℃, the water content and fresh weight of Tieling and Jinan population was first quick increse, and get the peak after 12 d developed, then did not differ significantly, but Changsha and Danzhou population’s still increase gradually. Dissect the diapause egg of different development period, and dicover the diapause egg of Tieling, Changsha, Danzhou population terminate development at 7th stage, but Jinan population terminate development at the 6th and 7th stage. Also detect the survival rate of different developmental stages at-10℃for 1 d, and find there were significant differences in different developmental stage in each population, and corresponding with diapause stage,7th stage has stongest cold hardiness.(2) Detect the 4 populations SCP (supercooling point) of Oxya chinensis Thunberg, the SCP of Tieling, Jinan, Changsha, Danzhou was-26.7±1.6℃、-25.5±1.2℃-23.4±3.0℃and-20.1±4.0℃respectively, SCP and latitude have a negative correlation that the higher the latitude is, the lower the SCP is. After treatment in different temperature below zero and time, the survival rate gradually decrease with the temperature reducing and the time increasing for each population, Tieling population has the longest time of Ltemp50 and the lowest temperature of Ltemp50, the next is of Jinan, then Changsha. Danzhou population has the shortest time of Ltemp50 and highest temperature of Ltemp50. So the results indicated the cold hardiness of Oxya chinensis Thunberg has significant geographic variation and the cold hardiness enhance with the latitude rising.(3) After different time and temperature acclimation between 0-8℃, Low-latitude Changsha and Danzhou populations have good acclimation effect, after certain time low temperature acclimation, the cold hardiness significantly increase. But High-latitude Tieling and Jinan populations did not get good acclimation effect.(4) The developmental threshold temperature and effective accumulated temperature of 4 populations were analyzed with the liner regression method and the optimum seeking method. And the result was that Tieling population has the lowest developmental threshold temperature 14.1±0.5 and 13.7±0.5℃, Jinan 15.8±0.5 and 15.1±0.6℃, Changsha 15.0±0.9 and 14.3±0.8℃, Danzhou 15.6±0.4 and 15.5＋0.4℃。The effective accumulated temperature of Tieling was 179.1±8.6 and 187.7±9.9 degree/day, Jinan 187.8±10.1 and 205.4±13.5 degree/day, Changsha 158.6±14.2 and 172.4±10.9 degree/day, Danzhou 194.3±8.6 and 197.3±10.9 degree/day. Both the development zero and effective accumulated temperature of these 4 poputions have geographic variation and the variation was related to latitude and voltine.
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