The characteristic of ground-objects spectrum is the basis of application of remote sensing. The imaging simulation principles of the optics image were described and a method using field measured endmember spectrum with higher spectrum resolutions was proposed to simulate spectrum of multi-spectrum images with lower spectrum resolution. The authors take the delta oasis of Weigan and Kuqa rivers as a study area, and choose vegetation and soil as study object. Firstly, we accomplished the simulation from field measured endmember for multi-spectrum by using the spectral response function of TM, and found the large correlation between simulated multi-spectrum and pixel spectrum of TM by using the statistical analyze. The linear model is set up to accomplish the quantitative transformation from endmember scale to pixel scale. Secondly, the translation relationship between the data computed from RS images and the data measured directly from the earth surface were analyzed. A method was proposed by using images with lower spectrum resolution to simulate images with higher spectrum resolutions.