The invention discloses a satellite remote sensing sensor in-orbit radiation calibration method, which specifically comprises: 1) acquiring radiation control point information; 2) cancelling geometric dislocation between images of adjacent cameras on the same orbit; 3) acquiring radiation connection point information; 4) constructing a spaceborne multi-camera splicing imaging sensor in-orbit radiation calibration model; and 5) calculating the in-orbit absolute radiation calibration coefficients of each waveband of the camera. Compared to the traditional in-orbit radiation calibration method, the satellite remote sensing sensor in-orbit radiation calibration method of the present invention has the following characteristic that the integrated treatment on the spaceborne multi-camera splicing imaging sensor in-orbit absolute radiation calibration and the correction of the relative radiation between the cameras can be achieved.