Liquid concentration plays an important role in many industrial processes. We designed a concentration detection system based on the principle of differential pressure, and introduced a turbulence elimination structure (TES) to improve the internal flow field. In order to explore the influence mechanism of the internal flow field on the detection, two models were used for numerical simulation under different working conditions. The results show that TES can effectively restrain the velocity fluctuation and turbulence intensity change of the flow field in the observation trough, thus forming a good measurement environment. The experimental results show that the measurement signal of the model with TES is more stable, and a stable detection area is formed between sensor 1 and sensor 3, which can be used for efficient detection of the sensor system. For the model with TES, the optimal speed range of 0.3–0.8 m/s was determined through experiments.