Stationary slewing crane1.Electric control equilibrium system is applied to avoid overload of switching and lift mechanism,Website:://.xqcranes.com, as a result of which,the outage rate can be reduced .2.The four bar linkage mechanism is optimized by dynamics software,when luffing,the horizontal move of load in ensured,the transmission angle is increased and the pressure angle reduced,by winch,the service lift of four bar linkage mechanism is increased.3.The luffing mobile counterweight is adopted so that when operating,the upsetting moment caused by load is minimized and the service life of revolving support increased.