In order to further clarify the difference of riparian landscape scale and its impact on river phosphorus (P), the relationship between landscape and river P at riparian scale was analyzed quantitatively. Based on long-term hydrological and water quality monitoring data, this study used redundancy analysis to clarify the relationship between landscape pattern characteristics at different riparian scales and river P concentrations in different hydrological seasons. Change point analysis was used to quantify the threshold range of the core landscape metrics leading to the abrupt change of river P concentrations in wet and dry seasons. The results showed that:(1) The effects of landscape pattern buffer zones on river P concentration have significant spatial scale characteristics, 300 and 400 meters are the critical scales affecting river P concentration in wet season and dry season, respectively. (2) SPLIT of farmland patches (SPLIT_farm) and LPI of residential land patches (LPI_res) were the core landscape pattern characteristic indexes that affect river P concentration in dry season and wet season respectively. When the SPLIT_farm exceeded 15.76~23.83 and LPI_re was less than 28.8%~36.5%, the abrupt probability of P concentrations in wet and dry rivers can be reduced respectively. The results can provide important theoretical basis for land use and landscape planning aiming at mitigating P non-point source pollution.