Numerical analysis method for influence of random shrinkage defect on mechanical property of casting

The invention relates to a numerical analysis method for influence of a random shrinkage defect on the mechanical property of a casting. The method improves the conventional random lattice models, establishes an algorithm for generating any one random shrinkage unit, and allows the algorithm to describe unique character of combination of random cloud aggregated distribution and random scattered distribution of shrinkage. The method can generate a group of numerical value samples (the number of the samples is designated by a user) of any two-dimensional random shrinkage defect, the generated samples can achieve the area, the shape and the location of shrinkage and are random; and the random samples can be further used for statistic analysis of the influence of the random shrinkage defect on effective mechanical behaviors (such as elasticity modulus and stress concentration factors) of the casing, and then the quantitative influence of the random shrinkage defect on the effective mechanical property of the cast