The fixed linear mirror solar concentrator and its working principle are introduced. It is necessary to culate solar beam radiation on each of tilted mirror for the design of solar collector system. Fixed mirror solar concentrator (FMSC) is an approximation which treats smooth linear optical reflector as broken into segments. The incidence angle and illuminate area of every mirror consequentially vary throughout the year, which makes the calculation of the beam radiation relatively complex. The equation of incidence angle, illuminate area and geometric concentration ratio are obtained by vector analysis. And the instantaneous solar beam radiation of whole mirror field is computed. Finally, the cumulated irradiation of overall system is obtained during the available work. Furthermore, two kinds of concentrator are compared, including installation on the south facing with slope of latitude angle and adjustment of a tilt angle one year (spring and summer use). Adjusting slope angle once a year, radiation from concentrator system with open width of 1800 mm increases by 6.53%, with an increment of 65.78 GJ/m.