Workers' Serious Disease Mutual-Aid Security is the important component of Workers' Mutual-Aid Security(WMAS)in China.Based on the theory of loss distribution,this paper designed actuarial model of serious disease.By the test of data,the premium of Special Serious Disease can be calculated by the Model 1,and the premium of Women's Special Disease can be calculated by the Model 2.And through the development of WMAS in Jiangxi province,the paper put forward three suggestions,which design age adjustment coefficient to control the incidence of a disease,find out the proper overhead expenses and risk coefficient,make a proper exonerative time.