To analyze the effect of laser cleaning and coloring process on the coloring quality of 304 stainless steel with rust layer, discuss the coloring principle, and provide theoretical and technological support for the one-time success of cleaning and coloring, this paper establishes the finite element model of 304 stainless steel with rust layer processed by nanosecond pulse laser by COMSOL Multiphysics, analyzes the influence of temperature field distribution and parameters on the surface ablation of the rust layer during the processing, guides the selection of coloring parameters, adjusts the test parameters to obtain the samples with good quality, measures the microstructure and energy spectrum distribution of the samples by scanning electron microscope and X-ray energy spectrometer, discusses the cleaning quality and color principle, as well as carries out the coloring test of 304 stainless steel with different roughness to analyze the effect of roughness on color display. The results show that the distribution of temperature field is related to the thermal conductivity of the material. When P = 20 W, h = 0.01 mm, v decreases and ablation depth deeps. In the four samples in yellow, blue, green and red, the oxygen content in the blue samples with the lowest energy density changed from 19.87wt% to 0wt%, indicating that all kinds of samples have been cleaned and can be colored to obtain smooth and high-quality surface. For the coloring sample with high roughness, the sample color is not distorted with the observation angle of 90°. One-time success of cleaning and coloring can be realized by optimizing the parameters. The color principle of 304 stainless steel by nanosecond laser is related to energy density. Undistorted coloring samples can be obtained through coloring 304 stainless steel with surface roughness Ra >1.6 μm.