In order to reduce the calculating amount and memory consumption of the Weighted Amplitude Wave Superposition method, and an improved method combines weighted amplitude wave superposition method and covariance proper transformation is used in this paper. On the basis, with the mode truncation criteria based on variance ratio, the reduced orders matrix of principal components of the cross-spectral density is employed to conduct the Cholesky decomposition. Furthermore, an error standard is defined to estimate the simulation precision. Practical algorithm is put forward and its efficiency can be enhanced by FFT. Finally, The simulation procedure is applied to an example and the results show that the proposed method remarkably saves the simulation time, the mode truncation criteria based on variance ratio is presented to improve calculation. the cross-power spectral density function, cross-correlation function are in good agreement with the expected targets. the procedure presented in the paper can be an accurate and effective method to simulate the stochastic wind field.