In order to study the parameter selection for slurry circulation system of slurry shield in complex strata, the calculation method of critical flow velocity of mud are adopted to calculate delivery and discharge volume of slurry required for soft ground stratum and hard and soft strata by taking Shiziyang Shield Tunnel for example; and the Fei Xiangjun model test formula is used to verified the results. And then the influence of different formation characteristics on delivery and discharge volume of slurry is analyzed by calculation results. The results show that: (1) The results of mud flow obtained by the two methods are almost the same, so as to prove the accuracy and rationality of the calculation methods. (2) The delivery and discharge volume of slurry should be increased to make muck transport smoothly in slurry pipe, and reduce wear of slurry pipe when tunneling in hard and soft strata. The results can provide reference for the construction of slurry shield in composite strata of similar projects in the future.