The visualization of ultra wide bandwidth synthetic aperture radar (UWB SAR) image data involves mapping from high dynamic range amplitude values to gray values of a lower dynamic range display device. In order to compress dynamic range of the UWB SAR image data appropriately, we examine several different dynamic range reduction techniques and come up to a new method with better visualization performance. This new arithmetical technique is analyzed based on the 3σ measurement and the amended mapping function. Compared with the original method, the new method has higher computational efficiency with the dark pixels are stretched appropriately and the bright details are well preserved.