Abstract: The phase matching protocol, which can break through the limitation of key capacity and has been proved by theory and practice, is a kind of twin-field quantum key distribution protocol. Aiming at the adverse effects of the finite data length effect in practical applications, the statistical fluctuation performance of the phase matching protocol is systematically analyzed. Using Gaussian analysis, Chernoff-Hoeffding bounds, and other statistical fluctuation analysis methods, the performances of the three-decoy and two-decoy phase matching protocols under different data lengths were simulated and analyzed combined with linear programming to estimate the relevant parameters. The simulation results show that the phase matching protocol considering statistical fluctuation can still break through the limitation of linear key capacity. When the data length reaches the order of 10¹⁶, the key generation rate and the maximum secure transmission distance are both close to ideal values. When the data length is less than or equal to 10¹³, adding decoy states cannot significantly improve the performance of the phase-matching protocol. As the data length increases, the performance of the system using the Chernoff-Hoeffding bound gradually approaches the performance of the system using the Gaussian analysis method.