Resistance identification of Saline-sodic stress was accomplished with 14 different mature types of rice varieties in northern China to understand threshold effect of saline-sodic stress on growth and development of rice. The result showed that survival rate of rice began to decrease when PH＞9.6. Although rice could regular heading and mature normally when PH was between 7.5 to 9.6,but with the increasing of saline-alkali stress,respective degree impact showed up on each agronomic character. Morphology threshold was defined at the PH value when inhibition rate of each morphology index reach 50%. LAI,yield and shoot number per plant got threshold effect earlier than survival rate and plant height. This indicated that large amount of uncertainty existed when determined saline-sodic tolerant with the change of morphology indexes. Yield threshold was defined at the PH value when yield inhibition rate reach 50%. The yield threshold of tested rice varieties lies between 8.9 to 9.6.