The invention relates to a Beidou deformation monitoring error testing device and a method thereof. The device comprises a control unit, a reference unit, a measuring unit, a mobile unit and a multipath simulation unit, and the reference unit, the measuring unit, the mobile unit and the multipath simulation unit are respectively connected with the control unit through lines, wherein the mobile unit is arranged on one side of the reference unit; the measuring unit is arranged on the mobile unit; the mobile unit drives the measuring unit to move horizontallyand vertically; the multipath simulation unit is arranged on one side of the measuring unit; the reference unit and the measuring unit are respectively used for measuring the theoretical position and the actual position of the Beidou antenna and sending corresponding position information to the control unit; and the control unit compares, analyzes and calculates the error between the theoretical position and the actual position; and the multipath simulation unit reflects the signal of the satellite to interfere with the measurement by the measurement unit. The Beidou deformation monitoring error testing device and the method thereof have the advantages that high-precision automatic control and simulation of deformation are achieved, high-precision sample data are obtained, deformation monitoring errors under static and dynamicmultipath environments are tested, and the precision of the positioning technology under different multipath environments is evaluated.