Abstract: Dynamic response speed is one of the most important performance indexes of catalytic sensor.Based on Fick’s diffusion theorem,the paper built a mathematical model of gas diffusion velocity for catalytic sensor in air flow,and studied influence of air flow on dynamic response of catalytic sensor through experiment.The study result indicated that speed of air flow and angle between air inlet of catalytic sensor and direction of air flow are two critical factors for dynamic response of catalytic sensor.The influence rule is the response time of catalytic sensor will increase,and the response speed and output value of catalytic sensor will decrease with an increase of angle between air inlet of catalytic sensor and direction of air flow,and the response time of catalytic sensor will decrease,and the response speed and output value of catalytic sensor will increase by increasing speed of air flow.