[Objective] The effects of landscape composition and structure on water quality at different spatial scales in Yangcheng Lake watershed were explored, in order to provide references for the water quality improvement and landscape pattern optimization.[Methods] Taking 12 water quality sampling points in Yangcheng Lake as the center, the circular buffer zones of 6 different spatial scales were generated by using GIS software. Landscape pattern index, redundancy analysis and Pearson correlation analysis was used to identify the most effective buffer zone of landscape pattern on wetland water quality, and explore its relationship with water quality.[Results] ① In general, the proportions of arbor forests and lakes gradually decreased at the spatial scale, while the proportions of urban residential land, paddy fields, and aquaculture ponds gradually increased. ② The spatial scale of the impact of landscape pattern on wetland water quality was reflected in different circular buffers, and the maximum explained variation was 68.2% in the circular buffer zone with a radius of 800 m. ③ Landscape composition variables only had correlation with water quality parameters in the circular buffer zone with a radius of 1 000 m. ④ Aquaculture ponds had a greater impact on water quality in a circular buffer zone with a radius of 200 m. Paddy fields, arbor forests and lakes had a larger circular buffer zone (radius greater than 500 m), which was the main landscape type affecting water quality.[Conclusion] The most relevant spatial scale between landscape pattern and water quality is 800 m circular buffer zone. The interpretation ability of landscape structure variables on water quality in buffer zones of different scales is more obvious than that of landscape composition variables. The correlation between water quality parameters and landscape pattern index in wet season is greater than that in dry season.