The invention discloses a testing device of flowing property characteristics of an internal combustion engine tee air inlet-exhaust pipe. The testing device comprises a testing part, pipelines, fans, variable-frequency motors, regulating valves, constant-flow flowmeters, sensors, constant-pressure barrels, transition pipes and a plurality of flexible pipes. Three end openings of the testing part are connected with three transition pipes which are connected with the three pipelines directly or through the flexible pipes selectively, and therefore switching of multiple tee pipeline connection methods is achieved. On and off of the regulating valves is selectively controlled to regulate air flow directions in the pipelines, two air flow types with the first end opening as a starting point or an ending point are achieved respectively, and therefore six flow types, comprising three branch flows and three integrated flows, of the tee air inlet-exhaust pipe are achieved, measurement of the flowing characteristics of the six flow types is achieved, the structure is simple, operation is flexible, and high universality is achieved.