The spectroscopic detection of ammonium (NH+4) has great significance. With the development of microfluidics, microfluidic spectroscopic analysis aiming at rapid, portable and multi-component detection has realized tremendous achievements. However, the excessive consumption of the indicating material which exists all the time has not been settled yet. Zinc porphyrin, being a natural chromophore, can reversibly detect NH+4 and settle the problem. But it suffers from the lack of selectivity. In allusion to these issues, a coupled microfluidic chip which consists of a reaction chip, a gas-diffusion chip and a detection chip is fabricated in our experiments. The reaction chip made of polydimethylsiloxane can convert NH+4 into NH3. The gas-diffusion chip which is made of two glass chips and a piece of polydimethylsiloxane gas-diffusion membrane allows NH3 diffuses into the detection solution. The detection chip immobilizes the indicating material tightly through the multi-layer structure. The indicating material fabricated by dying zinc porphyrin on the surface of the cation exchange resin permanently will turn from green to purple when it meets NH3 and will turn reversely into green when pure water is around. Using the coupled chip as the analytical platform, we set up a miniaturized spectroscopic detection system. With a portable spectrometer being the analytical instrument, we detect NH+4 by the transmission spectrum intensity change at the wavelength of 450 nm and study three factors that could affect the detection performance: the thickness of the gas-diffusion membrane, the flow rate and the dosage of the indicating material. First, we confirm the reversibility of the indicating process and settle the issue of indicating material consumption by the spectrum change intensity. The time responses show the rapidity of the indicating process. Then through the comparison to the contrast experiment, the high selectivity of the indicating process is demonstrated because the interference has no influence and the spectrum change is attributed merely to NH3. The relationship between the membrane thickness and the spectrum intensity change is obtained by changing the thickness of the gas-diffusion membrane in the gas-diffusion chip. Results show that the increase of the membrane thickness leads to a worse detection performance, but the outcome remains stable when the thickness is less than 10 μm. So 10 μm is selected as the optimal thickness in consideration of the mechanical strength. The impact of the flow rate is investigated afterwards. The results exhibit that the increase of the flow rate will decrease the spectrum intensity change, but the performance becomes unchanged when flow rate is less than 5 μL·min-1. Last, how the dosage of the indicating material impacts the results is studied. It is demonstrated that both excessive and inadequate indicating material will deteriorate the performance. So 5 mg is selected as the optimal amount. The spectroscopic detection system which uses the coupled chip as the analytical platform has the advantages of small volume, high economy, rapid response and realizes highly selective and reversible NH+4 detection.