For the problem of large chattering and difficult parameter tuning of traditional exponential reaching law sliding mode variable structure control, a new sliding mode reaching law is designed and fuzzy control is used to realize parameter tuning. In the double closed-loop DC speed regulation system, a speed regulator is designed based on the new reaching law. At the same time, in order to improve the efficiency of reaching law parameter tuning, an online tuning method of reaching law parameters is designed by using fuzzy control. The sliding mode parameters of the new reaching law are adjusted online by fuzzy control to improve the speed regulation performance of the system. The simulation model of DC speed regulation system is built in Matlab/Simulink, the results show that the new reaching law is superior to the traditional exponential reaching law in suppressing chattering and fast convergence, and the fuzzy control online tuning reaching law parameters is more efficient and performs better than the trial and error method.