Abstract: Based on conformal construction of the physical model in the three-dimensional orthogonal mesh system, an integral-based conformal convolutional perfectly matched layer(CPML) algorithm is given for solving the open port truncation problem when the enlarged cell technique combining with conformal finite-difference time-domain (ECT-CFDTD) method is used to simulate the wave propagation inside a hollow waveguide, and the algorithm has the same numerical stability as the ECT-CFDTD method. For the evanescent wave long-time propagation problems in a waveguide, several numerical simulations are done to analyse the reflection error by conducting sweeps of constitutive parameters of the integral-based conformal CPML. Numerical results show that the integral-based conformal CPML can be used for efficiently truncating the open port of the waveguide.