To solve the problem of long focal-plane-light-measuring time in ultra-high resolution CCD imaging system, an acceleration method is proposed. Pixel binning technology is adopted in this method to speed up the pixel output rate, the ratio of current integration time to minimum integration time is used as binning number of rows. In the light measuring period, the system uses the minimum integration time to expose the CCD, read out binned the pixel charge packets and calculate the average gray level and histogram for the auto exposure control arithmetic to use. This method can significantly reduce both integration time and pixel readout time, and maintain the original average gray level and histogram. The experiment results prove the performance of this method by compressing the light measuring time to 30% below. This method can be widely used in ultra-high resolution CCD light measuring process.