In order to analyze the combustion performance of inter-vane combustor, the design model of ultra-compact combustor is taken as the research object, and using Realizable k-ε  turbulence model and non-premixed PDF combustion model, the combustion flow field characteristics are simulated. Most of the fuel particles evaporate and mix at the top of the annular cavity, and the flame is connected on the bottom, thus forming the swirl combustion, then the high-temperature flame region appears in the rudiat slot. Radial slot structure and main jet entrainment affect the mixture of combustion products and main jet. Lean-fuel combustion conditions have a better combustion performance, and outlet temperature distribution lines of rich-fuel combustion are more similar to the ideal parabolic. Simulation results agree well with the experimental results under the same regular pattern condition.