The tertiary semi-diagenetic sandstone of the Wangjiazhai Tunnel on the Yunnan Linqing Expressway is characterized by loose structure, low diagenetic strength, and poor cementation. The geological disasters such as collapse, water gushing, and mud bursting are very easy to happen when the tunnel passes through the water-rich section. With the surface deep well dewatering of the tertiary water-rich semi-diagenetic section of Wangjiazhai Tunnel as an example, the surface deep well dewatering methods and key parameters for tunnel crossing the tertiary water-rich semi-diagenetic section were discussed. Based on the single well surface dewatering test, the groundwater level and strata permeability of the tunnel site were studied. According to the test, the permeability coefficient is 8.5 × 10^?4 cm/s, and the influence radius of single well dewatering is 60 m, which indicates that this area is a low-permeability formation. Based on the generalization of the aquifer in this area, design and calculation were carried out. The optimum spacing of dewatering wells is determined to be 15 m. The well sites in the test area were set up with the spacing of 15 m. The surface deep well dewatering effect was verified by observing the excavation of the tunnel and monitoring the pore water pressure of the surrounding rocks. The on-site verification shows that the water pressure around the tunnel face is reduced by about 70% after surface dewatering, which meets the safe excavation conditions. The construction progress is significantly improved, and the average monthly footage reaches 30 m.