Abstract: Based on the grey system theory, we replace the time response function of GM (1, 1) model for wave packet distribution, and obtain simulated evolution behavior of wave packet's wave function with mathematical techniques such as variational method, and make error analysis and correction. In practical applications, the approximate evolution behavior of wave function can be obtained with parameters of its development coefficient. Gaussian wave packet is taken as an example to show the method. The grey system theory in mathematical modeling is introduced into the calculation of physics, and an approximate calculation method is provided, which can be used in the calculation of wave packet evolution.