Corona is one of the critical technical problems in ultra-high voltage direct current（UHVDC）transmis-sion. Corona discharge is a complex physical process and has various influencing factors. Establishing numericalmodel based on the physical process of corona discharge is an effective means to research the corona problem. Coro-na fluid model has been widely used in the simulation calculation of corona plasma. However

most of calculations incorona fluid model using Kaptzov assumption as boundary condition do not have considering on secondary electronemission mechanism. Moreover

the effects of electron diffusion

charge recombination and photoionization were nottaken a full consideration when corona current was larger. In this paper

a comprehensive model based on the simpli-fied corona plasma fluid model has been proposed

which furtherly considers electron diffusion

charge recombina-tion

space photoionization and secondary electron emission mechanism. Meanwhile

the negative DC corona plasmain coaxial cylindrical electrode has been calculated by the Runge-Kutta method. Finally

the impacts of different fac-tors on the calculation result have been analyzed and the distribution regularities of negative DC corona plasma andcorona field have been observed. Secondary electron emission mechanism has larger effect on the result than the oth-er factors but the difference is less than 2% under 180kV.