A mathematical model is established to analyze the impact of positioning error of marker points on the calibration accuracy of mirror units for solar dish concentrators. The effects of individual and coupled positioning errors of three marker points on calibration accuracy are examined, and the maximum allowable positioning error is determined through a bisection method. Furthermore, the influence of different mirror sizes on calibration accuracy is analyzed by introducing the same positioning error in identical initial poses; a relationship between the mirror unit size and maximum allowable positioning error for calibration accuracy is thus revealed. Finally, the influences of different initial poses on calibration accuracy, under the same mirror size and positioning error of the marker points, are examined. The results indicate that the maximum allowable positioning error for calibration accuracy, considering coupled marker points, is 1 mm. Moreover, larger mirror units exhibit less sensitivity to marker point positioning errors. Optimal installation positions for points A and C are found to be close to -0.0087 rad, whereas, for point B, it should be close to 0.0087 rad. The proposed mathematical model for positioning error of marker points and calibration accuracy can be obtained using simulation results, independent of the geometric shape of the reflective mirror, thus reducing implementation costs and facilitating broad application in practical scenarios.