The modulation transfer function (MTF) is one of the key indicators to evaluate the signal transmission frequency characteristics of an optical imaging system, and the slanted-edge method is one of the important MTF measurement methods. To solve the problem that the traditional slanted-edge measurement method is not robust against noise, a new MTF measurement method based on the normal distribution fitting and median point estimate is proposed. A modified method that estimates the edge angle by fitting a two-dimensional function to the image data based on the normal distribution is proposed, the optimum slope angle and edge-spread curve of the actual image are calculated by using the method of looking up median point to the fitted image, and the edge-spead function (ESF) is achieved by using the Fermi function. The experimental result shows that the precision of the edge angle of the modified method is improved obviously when the noise of the actual image is relatively seriously, and the precision of the value of the MTF is also increased.