To study the influence of different quasi-isentropic loading modes on the ignition and the detonation growth processes of PBXs, a one-dimensional numerical model based on the DZK reaction rate model is presented, and then the parameters of DZK reaction rate model of PBXC03 can be experimental calibrated under the quasi-isentropic loadings. Moreover, the ignition and detonation growth processes of PBXC03 under different quasi-isentropic loading modes are simulated by using DYNA2D. It is found from the numerical results that both the increase of the peak pressure of shock front and the shock wave speed increase but the time to detonation decreases with the peak loading pressure, loading slope and curvature. It is also found that the explosive initiation process under the quasi-isentropic loadings can be divided into two stages: one is the initial stage that manifests mainly as the catch-up and convergence of the quasi-isentropic waves and the formation of shock waves; the other is the stage of shock initiation, in which a shock wave with a certain intensity is formed and grows gradually into a stable detonation wave. In addition, a necessary condition is proposed to discriminate the feasibility of an quasi-isentropic loading experimental calibration of the EOS parameters of a unreacted explosive, i. e., the sample's thickness must be smaller than the thickness of initial reaction.