The invention relates to the field of devices for measuring the NO2 concentration of high-sensitivity diesel engine emissions based on a TDLAS technology. The measurement device comprises a laser, a reference gas pool, a hollow-core optical fiber, an optical window mirror, a compressed air interface, a diesel exhaust pipe, a convergence lens, a laser detector and a data processing module. The reference gas pool is connected with the optical window mirror through the hollow-core optical fiber. The optical window mirror and the convergence lens are symmetrically distributed on two sides of the diesel exhaust pipe. The convergence lens is connected with the laser detector through the hollow-core optical fiber. According to the invention, the system structure is simplified by inserting the reference gas pool to omit a reference channel; during the operation of a diesel engine, original mechanical noise and low-frequency noise of an instrument are relatively large, which easily affects themeasurement; and the addition of the reference gas pool can effectively improve the signal-to-noise ratio of the device and improve the test sensitivity and accuracy.