This paper deals with the orientation workspace of a 3-PRS parallel manipulator. The manipulator is constituted by a fixed three frustum base, three incline guide rails, three P-R-S kinematic chains and a mobile platform. Based on the kinematic analysis, the orientation workspace of the 3-PRS parallel manipulator are analyzed. The three dimensional view of orientation workspace is drawn based on inverse solution of its positional problem and comprehensively considering the structural restraint. The impact of its geometric parameter on the orientation workspace is analyzed quantitatively. The work of this paper provides the basis for the design and the practical application of the parallel manipulator.