The multi-fiber shape sensor has important application value due to its high precision and anti- interference. The installation error of core fiber affects the measurement accuracy of the sensor but there is no universal calibration method in present sensor application. In this paper, an orthogonal calibration method is proposed to get the position parameters of each optical fiber. Based the calibration parameters, the shape measured can be reconstructed. Through digital simulation and sensor experiments, the measurement error of the multi-fiber shape sensor can be reduced to 1% of the traditional method.