The judge criterion of plastic shrinkage cracking for cement based material was studied through the testing of plastic tensile strength and plastic shrinkage capillary stress of cement mortar and concrete.The so-called critical capillary depth was built up on the assumption that the plastic shrinkage capillary stress of cement mortar and concrete must be bigger than or equal to the plastic tensile strength.The research results indicate that if the plastic shrinkage cracking index is less than or equal to 1.360,the fresh cement mortar or concrete would crack at water-losing condition,while if the plastic shrinkage cracking index is more than 1.360,the fresh cement mortar or concrete would not crack.