The invention discloses a treatment system and a treatment method for contaminated soil. The treatment system for contaminated soil comprises a pneumatic membrane structure, wherein one end of the pneumatic membrane structure is connected with a pressure control system and a ventilator by pipes, the other end of the pneumatic membrane structure is connected with a self-control and detection device by a circuit, the other end of the pneumatic membrane structure is also connected with a gas treatment device by a collecting pipe, the gas treatment device comprises a bag-type dust collector for primary treatment and an activated carbon adsorption box for secondary treatment which are connected by a gas exhauster, and an exhaust funnel is connected behind the activated carbon adsorption box. The pneumatic membrane structure is also provided with an inlet and outlet system, and the self-control and detection device is used for carrying out real-time online monitoring on the concentration of volatile organic gases generated by the pneumatic membrane structure and carrying out automatic control according to the detection data to ventilate the interior of the pneumatic membrane structure, so that the gas in the pneumatic membrane structure meets the national requirement.