Obtaining high-precision Doppler frequency for very weak signals in deep space exploration is challenging. A phase-locked loop (PLL) is a widely used high-precision Doppler frequency measurement method, and the arctangent phase detector is the most widely used phase detector. However, the arctangent phase detector cannot correctly identify the signal phase for signals with very low signal-to-noise ratio (SNR) and very high dynamic. Therefore, the arctangent phase detector is the key module limiting the weak-signal and high-dynamic tracking abilities of a PLL. This study proposes a new phase discrimination method in which the phase difference between the real and the reconstructed signals is obtained by using the coefficients of signal transformation. By replacing arctangent phase detector with novel phase detector, the high-dynamic and weak-signal tracking abilities of PLL are greatly improved. This method is expected to provide a good reference for radar, navigation, and other fields involving carrier tracking, and it provides feasible technical solutions for high-precision carrier tracking of high-dynamic and low-SNR signals on some occasions.