Radiometric calibration is one of the key technologies for quantification of satellite remote sensing information. A calibration method for high resolution optical remote sensor was presented based on small targets. At the same time, the reflectance test on site was changed to accurate measurement in laboratory. It substituted the field actual determination to the assumption of aerosol scatter. The atmospheric transmittance and at-sensor radiance could be calculated by simplified radiometric transfer code. And the approach could isolate the digital number(DN) signal created by little targets from response produced by background radiance through systems point spread function PSF estimation, which reduced the background requirement and improved the absolute radiometric calibration accuracy. The experimental results show that the calibration uncertainty is less than 3% for high spatial resolution satellite. The difference of calibration coefficient is less than 3.65% compared with large test site or gray-scale targets method. The small target approach is expected to achieve full dynamic calibration and geometric calibration in the full spectrum range for high resolution satellite optical sensor.