A multi-probe thermal gas flow sensor is designed based on assembled platinum-film probe.The flow field of the sensor in the pipe was simulated by FLUENT software at different flow development length.The simulation datas from the measurement points where the probes set are processed with the method of multi-sensor data fusion.The results of simulation show that the measurement precision of multi-probe flow sensor is much higher than single probe when the flow development length is not adequate and the flow field is not regular.