Resolution is the key index of microscopic imaging system, especially in the partially coherent light environment, the coherence degree will affect the resolution. In this paper, based on the Sparrow criterion, the relation between arbitrary coherence degree and limit separation degree is derived by forcing the second derivative of synthetic light at two points. Through linear regression analysis, a simple linear equation of coherence degree and resolution limit is obtained, and its accuracy is verified. In this paper, an imaging system of partially coherent light is designed, and the influence of different coherence degree on resolution limit is studied by MATLAB simulation. The experimental results show that the resolution limit is 1.25mm when the coherence is 0.6, and the error between experiment and simulation is less than 5%. The theoretical and experimental results are consistent, which shows that the method is feasible to calculate the two-point resolution of microscopic imaging system under different coherence degrees, and provides theoretical support and experimental basis for related research.