In order to meet the test requirements for low speed flow field, based on the seven hole probe velocity measuring principle, this paper designed a set of multichannel probe velocity measuring system by sevenhole probes, which is given a detailed design of the embedded hardware circuits,upper and lower computer software system. which is based on the Modbus communication protocol, improved the consistency of pressure measurement data through the pressure coefficient of sensor calibration. The probe calibration experiment was carried out in the low speed wind tunnel, by analysis the results of probe calibration wind tunnel experiment, the absolute error of the probe’s pitch angle and azimuth is 0.2o. On the basis of the results, this paper puts a further analysis on the probe aperture and sensor measurement errors to the effects of measurement results.