The invention discloses a precision detecting system of a motor vehicle emission temperature sensor. The precision detecting system includes an operation control module, a central control unit, a plurality of temperature transmission modules and an environmental parameter module; the operation control module comprises a control cabinet; each temperature transmission module comprises a temperature analog-to-digital conversion chip; and the environmental parameter module comprises an analog-to digital conversion module conversion chip, an environmental temperature and humidity sensor and a flow sensor, wherein the flow sensor is arranged at the opening of a motor vehicle emission pipe and is connected with the analog-to-digital conversion chip through a data cable, and the environmental temperature and humidity sensor is arranged at an external environment and is connected with the analog-to-digital conversion chip through a data cable. According to the precision detecting system of the motor vehicle emission temperature sensor of the invention, the performance of the temperature sensor is measured under a real vehicle working condition, rather than under a simulated condition. The system can detect exhaust flow, so as to detect and analyze the performance of the temperature sensor under different flow rates; the system can detect the performance of the temperature sensor on line in a real-time manner and can output a curve for researching and analyzing the performance of the sensor; and the system can simultaneously detect the performance of temperature sensors at a plurality of locations on an exhaust pipe.