Image simplification, which reduces the information content of an image to suppress undesired details such as noise, is a very important basic ingredient of a lot of practical applications. The simplification of human brain MRI (Magnetic Resonance Imaging) is one of essential pre-processing steps for medical researches and clinical applications. Usually, the process of image simplification requires multiple iterations of reconstruction. Therefore, the efficiency of the reconstruction algorithm is a key problem. This paper has proposed an efficient reconstruction algorithm for MRI brain image simplification based on downhill filter. The main contribution of this paper is to use the regional maxima concept to modify the initialization condition of downhill filter algorithm. Experimental results show that the efficiency of this algorithm is much better than that of fast hybrid reconstruction algorithm, and it can achieve good result when it is used to the contour extraction from the MRI of human brain.