Water inflow problem in underwater tunnel which is affected by many factors possesses highly complexity and nonlinear.The theory of genetic algorithms and BP(back-propagation) neural networks were introduced.Taking a practical engineering as an example,six main control factors were chosen in the analysis,such as the development degree of surrounding rock fissures,water yield property of overlaying aquifer,water pressure of overlaying aquifer,the depth of tunnel,the strength of the overlying impermeable laye...