This work develops a low-complexity method that integrates the inverse transform and downscaling. According to the application requirement, the reduction ratios of the frame length and width are adopted at the matrix computation of the inverse transform. Since a small matrix is employed to compute the inverse transform and downscaling, the non-zero high-frequency components are compensated at the spatial and frequency domains. As compared to the conventional methods, the proposed method with the frequency-domain compensation is demonstrated to have the least computational complexity under the similar decoded picture quality. Particularly, the proposed method can meet various downscaling ratios to accomplish low-complexity transforms for mobile video applications.