Image processing is a powerful tool for increasing the reliability and reproducibility of disease diagnostics. Magnetic Resonance Imaging (MRI) is one of the best technologies currently being used for diagnosing brain tumor. Brain tumor is diagnosed at advanced stages with the help of the MRI image. Preprocessing is an important process to extract suspicious region from complex medical images. Automatic detection of brain tumor through MRI can provide the valuable outlook and accuracy of earlier brain tumor detection. In this paper an intelligent system is designed to diagnose brain tumor through MRI using image preprocessing filters such as Wiener Filter, Lee Filter, Gabor Filter, Median filter and Mean Filter. This paper gives the analysis of selection of proper filter according to the required parameters for best result and at the same time their comparative study enhances the selection of proper filter as per requirement.