Whether the cascade speed control system can be successfully used in cranernot is an mioportant research topic for electric machinery engineers in rec-ent years.This paper analyses many probleme involved in the cascade speedcontrol detail,iin ncluding the power transfer relationship,the mechanicalcharacteristics and its fitting with the load characteristics,the calculationsofahe cpacitancet and the parameters of the (?)ariable current device in thisspeed control system,and others.This paper laso gives the comparison be-cascade spee een tehtwd control and the rotor resistance control methods.