The high voltage direct current (HVDC) converter has a certain dynamic reactive power regulation ability. Making full use of the reactive power regulation ability of the converter station can significantly improve the stability of the HVDC. In this paper,the adjustable capability of reactive power of HVDC during steady-state operation is studied,and the coupling characteristics of active power and reactive power are analyzed. Taking conference International des grands reseaux electriques (CIGRE) HVDC standard test model and Guiguan Ⅱ direct current transmission engineering model as examples,the operating range of direct current under steady-state condition is analyzed,and then the adjustable capability of reactive power on both sides of rectifier and inverter is obtained and applied in reactive power control. It is found that CIGRE HVDC standard test model has similar regulating capacity of capacitive reactive power and inductive reactive power,while regulating capacity of inductive reactive power is higher than that of capacitive reactive power in Guiguang Ⅱ direct current transmission engineering model. The application value of reactive power adjustable capability is verified in electromagnetic transient simulation program PSCAD/EMTDC.