According to the problem of bad uniformities of expanding beams for excimer laser of projected lithography which holds 90 nm exposure linewidth, a kind of reflective beam expanding unit is modified based on the principle that the beam edges of Gaussian type can be superposed to enhance uniformities. It is shown that there is a contradiction between the sizes of superposing beams and the transmission rate on some areas of the parallel-reflective beam expander, in that case the improved capacities for the beam uniformities are restricted. Based on the above analysis, a non-parallel reflective beams expanding unit is proposed. The relational expressions about output beam sizes, number of superposed sub-beam units and wedge angle between two mirrors are deduced and the span of wedge angle and the structure of beam expanding unit are determined based on the deduced equations. The proposed beam expanding unit is proved to be useful to achieve beam expanding, as well as to reduce the interfering speckle effects. And the uniformities of output beams is increase.