The problem of the calculation of the tristimulus value when the shape of the instrument function is slightly deviated from the symmetrical triangle is studied, and the corresponding optimal weighting table is explored. The results show that the optimal weight can be obtained by solving the linear equations of three coefficient matrices, and the coefficient matrices are symmetric positive definite tridiagonal matrices. The optimal weighting table method obtained in the previous study is extended to the case where the instrument function shape is asymmetric triangle. The simulation results show that the accuracy of the optimal weighting table method is better than that of the three-point and five-point calibration methods for the 10-nm and 20-nm measurement intervals. For the measurement interval of 5 nm, the best calculation method is to conduct three-point correction of the measurement data first, and then use the direct selection method to calculate the tri-stimulus value.