Guanmen subsea tunnel in Zhoushan is the key work of the project connectiing Daishan County and Zhoushan Island. The tunnel crosses Guanmen watercourse. The geological investigation reveals that the average depth of the water at the tunnel site is 35 m, with the maximum depth reaching 53.8 m. The sea bed at the tunnel site fluctuates dramatically and the water depth varies greatly. Furthermore, there are 3 largescale fracture zones at the tunnel site, where the rock conditions have great impact on the tunnel. In the paper, comparison and contrast is made between two subsea tunnel options, i.e., subsea tunnel constructed by drill and blast method and that constructed by shield machine. In the end, the option of subsea tunnel constructed by shield machine is proposed.