The quality of image includes the resolution of pixel and contrast of the pixel. The better the quality of microwave image is with higher the resolution of image pixel and larger the image contrast. The contrast depends on the signal to noise ratio of the radar receiver. The resolution of pixel depends on the radar frequency. The higher the frequency the better the resolution of pixel will be. Unfortunately, the higher the frequency the smaller the signal to noise ratio will be. The phenomenon will cause the lower image contrast. In this paper, the formulation of microwave imaging, quality of radar image with various frequencies and number of transceivers are detail discussed. In order to obtain the better quality of image, a new technique with multiple frequencies is developed. The results of microwave image with better resolution and higher contrast by both simulation and measurement are agreed.