The invention discloses a method for identifying the roughness of a water conveyance channel of a long-distance water transfer project based on genetic algorithm, relating to the determination of hydraulic design parameters. The method for identifying the roughness of a water conveyance channel of a long-distance water transfer project based on genetic algorithm comprises the following steps: confirming the objective function and the solution of the problem; performing initialization and obtaining the initial population; calculating the water level after the upper gate of a plurality of working conditions corresponding to each roughness value in the initial population by means of one-dimensional hydraulic simulation model, and then calculating the fitness; judging the termination condition, and if the termination condition is satisfied, the roughness is the optimal solution; if the termination condition is not satisfied, performing selection operation and crossover operation on the initial population successively, calculating the fitness, and judging the termination condition once again, and if the termination condition is satisfied, the roughness is the optimal solution; and if the termination condition is not satisfied, then performing mutation operation on the initial population which is performed crossover operation, calculating the fitness, and judging the termination condition once again, until the optimal solution of the roughness value is obtained. According to the invention, the hydraulic model is combined with the genetic algorithm to identify the optimum value of the roughness of each channel and pool.