The orbital angular momentum of the partially coherent radially polarized vortex beam is applied to the focal field target detection.Based on the partially coherent and the Richards Wolf vector integral theory,the optical field distributions in the focal field target plane of the beam are derived.The distribution characteristics of the orbital angular momentum density in the focal plane are discussed.The influence of the coherence length of incident beam and the numerical aperture of focusing lens on the orbital angular momentum density distribution and the orbital angular momentum of the longitudinal component is analyzed.The results show that with the increase of the coherence length,the orbital angular momentum and the orbital angular momentum density rapidly increase.When it increases to 0.5cm,the changes of the orbital angular momentum and the orbital angular momentum density tend to be flat.Thereafter,the change of the coherence length no longer affects the orbital angular momentum and the orbital angular momentum density distribution.As the numerical aperture increases,the orbital angular momentum and the orbital angular momentum density always show a growing trend,and the change extent becomes larger after the numerical aperture is greater than 0.7.