Pressure adjustment of wind tunnel for sand and dust test is different from general circumfluent one. In order to determine characteristics of pressure variation, dynamic model for controlling-pressure point, testing port andinjecting-sand-and-dust port was established, by the means of lumped parameter method(LPM) with physical analysis and simplification. Control method was offered according to the model. The rule that different disturbance effects on pressure distribution was observed, and control system of wind tunnel for sand and dust test was studied by the means of simulation. The results are satisfied. This work is important to optimize the configuration of the wind tunnel and to enhance its ability of sustaining pressure and is significant to ascertain the control precision for each component of the wind tunnel.