In order to provide the external heat flux of space camera accurately, a method was proposed to calculate the instantaneous external heat fluxes of a space camera with changing attitudes frequently depending on its position in the Geomagnetic Coordinate system(MAG). First, in J2000 Coordinate the relative position of the sun, earth and radiation intensity of sun was calculated. Second, geomagnetic latitudes of a camera and orbital times when camera entered or exited from high geomagnetic latitudes(L≥60°) were calculated. Then, the camera′s attitudes were ensured with geomagnetic latitudes. Finally, orbital view factors of six mapping planes were achieved by the Monte Carlo Method(MCM)and the instantaneous external heat fluxes was obtained during the on-orbit time. The external heat fluxes of this paper were consentaneous with the software IDEAS/TMG. Compared with the stable attitude camera, the attitude varieties of the camera take a relatively strong influence on the external heat flux, especially for the +Z-direction where optical entrance is located. The fluctuation range of the +Z-direction external heat flux is about 0-1 245.4 W/m2.