An optimized method was proposed for in-flight spectral calibration of unmaned aerial vehicle (UAV) hyperspectral imager in visible and near infrared band. Taking simulated radiance as a reference spectrum, the method uses spectrum matching technique to retrieve the most important spectral parameters of center wavelength and bandwidth. With the data in Urad Front Banner, Inner Mongolia on November 14th, 2010, hyper-spectral camera on UAV was calibrated based on the laboratory spectral calibration result. The efficiency of data process was 100 times that of normal algorithm. A method of accuracy evaluation with ground targets was also developed. The in-flight spectral calibration accuracy for a sensor with bandwidth of 7nm was proved to be better than 0.5nm.