The roadheader hydraulic system is supplied with oil by the quantitative pump.The system relies on the center function of reversing valve to unload.The traditional system consumes more energy.The spool design of reversing valve is complex.In response to these problems,the oadheader arm lifting load sensing system was designed.The load sensitive variable displacement pump model,HCD model of the reversing valve and roadheader arm plane mechanism model were verified.The roadheader arm lifting load sensitive control system was built.The middle unloading performance of the roadheader arm lifting system was analyzed.The influence of the balance valve pilot ratio,the hydraulic cylinder size,the main valve core throttle area of oil return in large chamber of hydraulic cylinder on the arm lifting performance was studied.The results show that:when the reversing valve is in the middle position,the center unloading valve of the system is opened and the pump is under low pressure unloading condition;when the cylinder diameter of the arm hydraulic cylinder,the balance valve pilot ratio and the back pressure of BSymbolnB@T return oil are increased,the starting impact of rocker arm falling increases;when the balance valve pilot ratio is 1.0,the arm hydraulic cylinder diameter is 160 mm,and the return oil throttling area of B→T is 24.68 mm2,the arm descending starting impact is small.