In view of the water and sand inrush risks faced by large-diameter slurry shield during launching and receiving in the water-rich silty fine sand stratum in the offshore area, the engineering practice of the double-lane shield tunnel at the bottom of the Karnaphuli River in Bangladesh was analyzed. The reasonable ranges of the tunnel portal chiseling thickness and the working shaft end reinforcement length were studied by theoretical calculation and numerical simulation. Finally, the reinforcement effect was evaluated through the analysis of shield tunneling parameters. The research results show that the reasonable range of longitudinal reinforcement of the end of the working shaft in the water-rich sand layer can be obtained by adding 2?3 m to the length of the shield body. The comprehensive measure of sealed steel sleeve + triple tube high-pressure rotary churning reinforcement + well drainage + curtain for water sealing by grouting can effectively reduce the risk of water and sand inrush during the shield launching and receiving, and it has a high safety factor with good economy. The chiseling thickness of the diaphragm wall at the tunnel portal is 60 cm, which can ensure the safety of the tunnel portal and the construction progress.