The curvature spectrum causes the light energy within one spectral line cross several CCD pixels in minitype spectrometer and decreases the resolution and sensitivity. To solve this problem, a special vertical binning method for area image sensor is proposed. During the vertical binning, the position of the electron package is moved in CCD horizon register. The energy center of the same spectral line is always kept in the same electron package. Experiment has shown this method as achievable and effective. The FWHM of Hg 576.960nm spectrum has been reduced to 0.21nm from 0.27nm and the peak intensity increased to 38513ADU from 28428ADU.