In order to effectively reduce the cracking of mortar, this paper analyzes the cracking prediction equation of mortar, determines the "new method of cracking reduction" from the level of material composition and constraints, and verifies the scientific effectiveness of the new method of cracking reduction in different environments from the theoretical and experimental levels. In order to improve the practical value of the new method of crack reduction, to the methods of reducing constraints, such as applying grease application, laying plastic film and wrapping 3mm retarding slurry between plastic films were explored. The results show that the new cracking reduction method of reducing the water-cement ratio, reducing the restraint degree and increasing the sand-cement ratio can significantly improve the crack resistance of mortar. The way of wrapping 3mm retarding slurry between plastic films can reduce the restraint of wooden mold mortar by 66%, and the crack reduction effect is obvious.