To optimize the combustion performance of solid propellants and enhance the combustion stability of solid rocket motors （SRMs）， an integrated combustion response model for four-component hydroxyl-terminated polybutadiene （HTPB） propellant with microcosmic heterostructure is established. The improved combustion model that considers the microstructure of four-component propellants is developed based on the heterogeneous quasi one-dimensional （HeQu1-D） framework， incorporating both the micro-scale heterogeneous structure and the unsteady heat transfer process. The model is well verified against experimental data from T-burner tests， with a maximum error of 5.34% in combustion response. Furthermore， the effects of component content distribution， particle sizes， and external environmental conditions are investigated under a working pressure of 12 MPa and excitation frequencies ranging from 250 to 2000 Hz. The results demonstrate that adjusting the particle sizes of AP and NA can significantly alter the propellant''s combustion response characteristics， where smaller AP particles combined with larger NA particles are more conducive to stable combustion. Regarding component content， increasing the relative proportion of AP helps reduce the pressure-coupled response function of propellant. When 10% of AP is replaced with RDX， the pressure-coupled response function exhibits a peak-value increase of 0.15 accompanied by a 25 Hz reduction in peak frequency. More pronounced effects are observed with HMX， where the same 10% of AP replacement leads to a greater peak value enhancement of 0.43 and a more substantial peak frequency decrease of 85 Hz. This work contributes to understanding the mechanism of combustion instability and provides guidance for efficient optimization of propellant formulations.