To validate the radiometric performance changing of GF-2 satellite, and obtain reliable on-orbit calibration coefficients of GF-2 sensors, an in-situ calibration methodology based on wide dynamic ground target is presented. Based on Dunhuang Gobi site, a test site including high, middle, and low reflective characteristics is re-selected and established. After that, the first on-orbit calibration for GF-2 is performed using the reflectance-based method and field measurement campaign. At last, the calibration coefficients changes and influence by comparing with prelaunch laboratory calibration results is discussed. The results indicate that: 1) the system offset of GF-2 itself is close to zero and relatively stable, while the radiometric responsivity has changed; 2) the calibration coefficients by using multi-site calibration method can better characterize on-orbit performance of GF-2 compared to the prelaunch lab calibration; the new calibration coefficients can be used for quantitative products retrieval and systems performance evaluation.