Off-axis Three-Mirror-Anastigmat(TMA)optical system is a most advanced optical system used in space cameras for earth observation presently. In this paper,the imaging mechanism of a off-axis TMA wide viewing field space camera is analyzed, and two kinds of calibration projects, sectional viewing field radiometric calibration and entire viewing field radiometric calibration using an especial hatch integrating sphere,are proposed according to the path and construction features of the off-axis TMA optical system.Then, Both the projects are used in the laboratory radiometric calibration for the different phase specimens of the off-axis TMA space camera. The calibration result indicates that both of the projects are feasible and can fully satisfy the requirements of laboratory radiometric calibration. The service conditions of the two projects are obtained by analyzing the relative merits of the projects. It is concluded that the calibration accuracies of two projects are 1.68% and 1.89%,respectively.