Abstract: In the image fusion methods which are based on multiscale transform, the lowpass subbands are usually fused through a weighed sum rule, this may lead the intensity of the fused image to a balenced level, some bright or dark objects will not preserved especially when the two source images are taken from different types of sensor. This paper proposes a total variation method for the optimization of lowpass weight function, which can be built on either image domain or transform domain. Several multiscale transforms are chosen to verify the proposed method. Experimental results show that the method can obtain delicate and precise optimized weight function, and preserve the intensity of salient objects well, thus improve the visual quality of the fused image. Moreover, this method can be applied to any kind of multiscale transform based image fusion.