Abstract: In recent years, the micro-pollution problem of excessive organic matter and ammonia nitrogen concentration in urban water caused by rainfall runoff has become more prominent, affecting urban human settlements and ecological environment. It is urgent to develop green and efficient in-situ treatment technology to meet the needs of micro-pollution urban water quality improvement. The front pond of the urban rainwater lifting pump station was selected as the water body for treatment, and a cyclic assembled wetland composed of power module and efficient module was set in situ in the water body. Through the water body circulation treatment of the front pond of the pumping station, the efficient removal of pollutants and the improvement of water body self-purification capacity were realized. Through the continuous monitoring of water quality parameters (COD, ammonia nitrogen, turbidity) of different modules of assembled wetland and the determination of oxygen consumption rate and ammonia nitrogen elimination rate in different areas of the water body, the influence of recycling treatment of assembled wetland on the water quality improvement of urban micro-polluted water bodies was explored. The results showed that: (1) During the stable operation phase, the removal efficiency of COD and ammonia nitrogen was 85% and 87%, and the effluent of COD and ammonia nitrogen was 2-3 mg/L and 0.2-0.3 mg/L, respectively. (2) Under the cyclic treatment of the assembled wetland, the oxygen consumption and ammonia nitrogen removal rates of the water body of the front pond were increased 3-10 times and 2-3 times, respectively. (3) A microbial community with efficient denitrification and carbon removal capabilities was established on the surface of the wetland's fill material, ensuring the pollutant removal performance of the wetland. The recycling assembly wetland treatment not only utilized the filtration, plant uptake, and microbial degradation processes inherent to remove pollutants, but also improved the self-purification capacity of the treated water body by strengthening gas-liquid mass transfer, increasing dissolved oxygen levels, and accelerating biochemical reaction rates. The assembled wetland recycling treatment technology has the potential to be popularized and applied in the purification of urban rivers and lakes and the improvement of water microecology.