For a trough solar collector array with single-axis tracking, shadow effect between collector units is always inevitable. In this paper, the shading geometric models of North-South oriented and East-West oriented trough collector arrays are established, and the general calculation formulae of the shading rate are derived. By taking array made of trough collector with aperture width w=3m and length L=20m as example, the variation of the shading rate ηs with the installation distance Lcc (the distance between the two adjacent trough collectors), solar time tS and the day number of the year N are calculated, and the shortest installation distance are analyzed and discussed. The research results can provide valuable reference for the optimization of arrangement of trough solar collector arrays (especially arrays in limited field area).