Abstract: In order to accomplish the wind speed control system for a FDxx wind tunnel,a PID parameter setting method based on adaptive online genetic algorithm was designed.In the case of the limited gas source for a wind tunnel test,the algorithm can quickly establish the flow field and ensure the stability time of the flow.First,joint coding is done with these parameters. With elitist strategy adopted in early genetic evolution stage,a non-linear selection method based on roulette selection is introduced in the last period.So optimum individuals are preserved and the population diversity is increased.The fixed value thus would not be exceeded in the dynamic adjustment process.The objective function is set up with the error absolutes and variation rate accompanied by penalty functions.When the fixed value is exceeded,the excess is taken as the optimal.This method has been applied in a field debugging of FDXX wind tunnel.The result shows that it is fast,effective and reliable to use online adaptive genetic algorithms to set the PID control parameters.