[Objective] The water quality changes along the way in the compound ecological ditch system and the system’s purification effect were studied in order to provide a scientific reference for the rational construction and green development of a recirculating aquaculture model of rice-fish co-cropping. [Methods] After constructing a composite ecological ditch system connected by different types of ecological ditches, we sampled and monitored water bodies along the river in 2020 and 2021, and studied the purification effect of composite ecological ditches on aquaculture wastewater and paddy field drainage water. [Results] In 2020, the phosphate removal rate, nitrite nitrogen removal rate, and ammonia nitrogen removal rate of aquaculture wastewater were 96.21%, 91.27%, and 94.75%, respectively. In 2021, the phosphate removal rate, nitrite nitrogen removal rate, and ammonia nitrogen removal rate of aquaculture wastewater were 68.96%, 61.36%, and 51.92%, respectively. The water quality met the class Ⅳ standard specified in the environmental quality standards for surface water (GB3838-2002) after the paddy field drainage was purified. [Conclusion] A compound ecological ditch was used to purify and recycle aquaculture wastewater and paddy field drainage water.