The nonideal random property of the pseudo code should be taken into account to analyze the code tracking error accurately in the present of partial-band interference. A precise power spectrum model of the code was introduced, and the tracking errors obtained by simplified spectrum and precise spectrum were compared for different interference bandwidths. The REC(Relative Error Coefficient) was defined to quantitatively describe the effect of nonideal random property on the tracking error. If the interference bandwidth is larger, the REC will be smaller, and the effect of nonideal random property on the tracking error will be smaller, then the analysis results based on simplified spectrum and precise spectrum will tend to agree. When the REC is smaller than 0.2, the minimum interference bandwidths are presented for GPS L1 C/A codes. The bandwidths are the bounds of the application scope of the analysis based on simplified spectrum. Research results indicate that: if the interference bandwidth is larger than three hundred times of the frequency of the code period, the change of the code tracking error induced by the nonideal random property can be neglected. Conversely, the analysis based on precise spectrum will be necessary in the study of code tracking precision.