High voltage DC（HVDC） transmission always used in long distance power transmission， and has higher possibility of line fault than short line. Based on the operation of HVDC projects in China Southern Grid and State Power Grid， DC line fault recovery（forced retard） is analyzed. The shortcomings， such as only one pole enable force retard function， and fault range that can initiate force retard is small， are presented. Enhancing HVDC control software function is one solution to this problem. If one pole is in pole block sequence， or during line fault， or in force retard sequence， force retard function of the other pole is disabled. By this way， two poles force retard or block simultaneously can be avoided， and force retard function is not limited by software anymore. Meanwhile， electrode line fault and metallic return line fault occurs， related HVDC protection function， such as electrode balance protection（60EL） and DC line transversal differential protection（87DCLT） should initiate force retard instead of pole block.