The focusing properties of partially coherent Bessel–Gaussian beams passing through a high-numerical-aperture objective are studied based on vectorial Debye theory. Expressions for the intensity distribution, degree of coherence $\mid \mu \mid$ , and degree of polarization P are derived near the focus. Numerical calculations are performed to analyze the influences of varying corresponding parameters on the intensity distribution, $\mid \mu \mid$ , and P in the focal region. It is shown that the intensity, $\mid \mu \mid$ , and P in the focal region are all influenced by varying the effective coherent length $L_c$ of incident beams and maximal angle α determined by the numerical aperture of the objective. Also, the linearly polarized incident field is found to be depolarized after it is focused by a high-numerical-aperture objective.