Abstract: In this paper, a curvilinear coordinate system immersed boundary (IB) method is proposed for flow simulation in multi-connected domains, which improves the solution efficiency by reducing the proportion of solid marked areas in the computational domain. The local encrypted geometric model contains many critical locations for small-scale structures. The method is combined with the Large-eddy Simulation-Transported Probability Density Function model (LES-TPDF) to simulate the turbulent combustion of a double-swirling combustor and a single-head model of a specific type of annular combustor to verify the method. In the case of a double swirl combustor, the simulation results show that the curvilinear coordinate system IB method can accurately analyze the flow field and combustion field structure behind the swirler, with a root mean square error of the peak speed of 6.6%. In the single-head combustion chamber simulation, the computational resource consumption of the IB method in the curvilinear coordinate system is reduced to 42.9% of the traditional Cartesian coordinate system immersion boundary method under the exact grid resolution. The root mean square error of temperature distribution is 11.7%, which meets the requirements of high-fidelity simulation of complex geometry combustion chambers. Based on this method, the two-phase turbulent combustion phenomenon in the actual combustion chamber with a complex structure can be simulated accurately and efficiently.