In order to know the influence caused by the original mechanism errors for the position-stance outputs, and take measures against eliminating errors and improving the precision, this paper worked out error analysis and error compensation for 3T-1R 4-DOF parallel robot mechanism. Based on the positional inverse solution model, the error model and the computational error procedure for the mechanism were established. The error simulations and quantitative analysis were carried out when errors were aroused from original errors of the structural parameters and driving parameters. The error forward and inverse resolutions were used in carrying out the position-rotation parameters workspaces and the joint workspaces compensation in software compensation technique, and the error compensation algorithms were introduced. The error compensation examples proved that two error compensation procedures are dependable and useful.