In order to study the effect of horizontal rotary jet grouting pile plus advanced small pipe combination pre-reinforcement in the rich water sand layer tunnel, based on a section of the Qingdao Metro tunnel, the finite element numerical simulation method was used to compare and analyze the reinforcement effect of three working conditions: non-pre-reinforcement, using horizontal rotary jet grouting pile alone, and rotary jet grouting pile combined with advanced small pipe combination pre reinforcement. The results show that compared with the non-pre-reinforcement scheme, the use of horizontal rotary jet grouting pile pre -reinforcement alone can reduce surface settlement, arch settlement, and longitudinal displacement of the palm face by about 61%, 59%, and 38%, respectively. The combination of horizontal rotary jet grouting pile and advanced small conduit pre reinforcement scheme can reduce surface settlement, arch crown settlement, and longitudinal displacement of the palm face by about 66%, 77.6%, and 38.9%, respectively. The groundwater seepage flow at typical excavation sections and arch feet can be reduced by 93.4% and 96.7%, respectively. The pre-reinforcement effect and water stop effect are significant.