In recent years, the problem of oil and gas pipelines passing through environmentally sensitive areas has become increasingly prominent. For oil and gas pipelines river-crossing tunnels in environmentally sensitive areas, the safety distance between the connecting pipelines at both ends of the tunnel and the environmental sensitive points, the safety distance between the tunnel and the environmental sensitive points, and the reasonable buried depth of the tunnel in the river bed are the key points to decide whether the oil and gas pipeline can safely pass through the environmentally sensitive area. Therefore, the reasonable and compliant design of river-crossing tunnels for oil and gas pipelines in environmentally sensitive areas is of great significance for ensuring the safety of project construction and operation. This paper takes the Daxi tunnel of Zhejiang‘s “county-county access” project as a study example. According to relevant laws, regulations, standards, and engineering practices, the safety distances between connecting pipelines and tunnels and various environmental sensitive points are comprehensively analyzed, and the safety assessment based on safety indicator control is adopted. Using engineering experience, numerical analysis, and theoretical calculation methods commonly used at home and abroad, and combined with the hydrogeological conditions of the riverbed section, the reasonable buried depth of the riverbed section of the Daxi Tunnel is determined. The results show that the design of plane crossing axis and longitudinal section crossing stratum of Daxi tunnel is reasonable, as it ensures the safety of construction and operation, and saves project investment. This research results can provide reference for the design of oil and gas pipeline river-crossing tunnels in similar environmentally sensitive areas.