Abstract: To detect the concentration of nitrite in microfluidic chip, a rapid detection method based on image analysis was proposed. In the microfluidic chip, the two-stage reaction cell was designed to carry out the primary reaction and chromogenic reaction of nitrite respectively. The image was collected and processed when the chromogenic reaction was completed, then the chromogenic reaction area was extracted, and the relative gray value was calculated to characterize the concentration of nitrite. It was found that there was a linear relationship between the gray value of chromogenic solution and the concentration of nitrite when the nitrite concentration range from 0.5 to 10 mg/L. The coefficient of determination was 0.9927, the detection limit was 0.8 mg/L and the detection time was less than 10 min. When this method was applied into the nitrite detection of tap water and bacon, the recovery rate was 94.1%~108.0%. The method proposed in this study extended the detection method of solution concentration in microfluidic chip, has convenient, speedy and accurate features.