Abstract: the largest prototypes of extreme load coefficient for a variety of flights have been obtained from pretreating extreme load data of flight tests and field surveys.Different mathematical patterns of distribution,such as Normal Distribution、Weibull Distribution、Pearsun Distribution、Rayleigh Distribution and Gumber Distribution,are applied to calculation,from which are derived both probability density function and probability distrbution function in each of these patterns.By means of recognition algorithm of Fuzzy Mathematics,approximation grades of the different patterns to the prototypes are determined.Then a reliable distribution regularity of the extreme load coefficients is provided for strength and reliability analyses of the aeroengine.