Based on the theory of non-imaging optics,the geometric parameters of light-emitting diode (LED) parabolic reflector and the impact of rotation angle of LED around the axis which is perpendicular to propagation direction on the efficiency of light collection are analysed in energy transfer aspect,and eventually unified closed relationships between efficiency of light collection of a parabolic reflector with the geometric parameters and the rotation angle are established. The results show that using étendue to evaluate the efficiency of energy collection of LED parabolic reflector is reasonable,and rotating the LED can further improve the efficiency,and for each different sets of geometric parameters,the best rotation angle is different. The simulation results are according with the theoretical analysis.