Monitoring the presence of multiple peaks in cross ambiguity function (CAF) and abnormal changes in automatic gain control (AGC) values are two common methods for spoofing detection. However, it is found that the combined performance of these two methods and their respective detection ranges of spoofing signal power have not been fully analyzed and verified. In this paper, a detailed statistical analysis of CAF monitoring under spoofing attack is conducted, including the signal-to-noise ratio (SNR) detection threshold, detection probability, elevation of noise floor and theoretical detection range of spoofing signal power. Besides, in order to make up for the performance degradation of CAF multi-peak monitoring in high-power spoofing scenarios, null hypothesis significance testing by P-value is applied to AGC gain measurements, the threshold of P-value and its detection performance are tested. Finally, a set of experimental tests are conducted to verify the correctness of theoretical analysis.