In this thesis we perform direct singularity analysis for the 3-CRU parallel manipulator, which is a three degree-of-freedom manipulator for pure translation. In order to locate direct singular positions, we begin by expressing the determinant of the Jacobian matrix Jx in terms of position of the center P of the moving platform. The Z and the Y coordinates of P may be chosen from the workspace, then the determinant of Jx is now a six order polynomial of X, the x coordinate of P. The direct singular positions corresponding to (Y, Z) are obtained by solving the polynomial equation, and retaining all real roots in the workspace. Direct singular positions so obtained are substituted into the Jacobian matrix Jx to verify results. All direct singular positions may be located by the method described above. In this thesis we show distribution of direct singular positions in the workspace and also several singular configurations.