Abstract: In order to model the probability density function (pdf) of radar clutter, which has some non-gaussian features, i.e., peak, asymmetry and heavy tail, the extended K-distribution random variables are obtained through multiplying the product of two independent rayleigh variables by generalized X~2 distribution random variable with n degrees of freedom. This pdf of extended K-distribution has more significant peak and heavier tail than that of previous K-distribution with the help of the product of two independent Rayleigh variables, whose effect corresponds well with the scattering mechanism of clutter of high resolution radar. Besides, the model of Markov diffusion process is used to generate correlated random variables of the extended K-distribution. The simulation results of the above pdf correspond well with the theoretical value.