There are errors between the theoretical values and the actual values for the parameters of type-Ⅳ concave holographic grating during its recording and using process, which will affect the spectral performance of the concave holographic grating. A simple grating optimization function which can be used to describe the spectral width is derived from the Fermat′s principle and a comparison to the root-mean-square (RMS) optimization function which is complex and disable to describe the spectral width is made to justify its validity. The errors are divided into two categories by their location relative to the reference plane and a quantitative analysis of their effects on the spectral performance of type-Ⅳ concave holographic grating is made. The results indicate that the error of one recording parameter or using parameter in the reference plane can be compensated by adjusting other recording parameters or other using parameters, and the recording parameter errors can be compensated by adjusting the using parameters when the grating constant is not changed; the compensation for the parameter error outside the reference plane can only be made by adjusting other parameter′s distance from the reference plane.