To achieve on-site analysis and emergency analysis of water quality indicators, a dual-channel portable analysis device was designed based on the Griess method combined with beam splitter prism. 3D printing technology was used to print the device’s housing, reducing the size and weight of the device. The experiment verified that the optimal LED constant current control current was 4.31 mA, and the data processing method was the median average method of five times absorbance data. The performance indicators of the device were analyzed. The results showed that the device’s weight was 552.6 g, the average power consumption was 0.13 W, and the detection limit of nitrite was 0.002 mg/L. The device has the characteristics of low cost, small size, high linearity, high sensitivity, and high stability. The analysis of 21 samples by the device showed that there was no significant difference with the results analyzed by the Griess method, indicating that the device can be applied to the analysis of nitrite in surface water reliably.