Understanding phosphate adsorption characteristics and establishing critical thresholds for phosphorus (P) loss risk in greenhouse vegetable soil are crucial for developing scientific fertilization strategies and improving P use efficiency. This study investigated topsoil (0-30 cm) and subsoil (30-60 cm) soils from solar greenhouse with cultivation durations of 1, 10, and 20 years, as well as plastic greenhouse with 5 and 15-year cultivation histories in Shouguang City, Shandong Province, to analysis of P adsorption characteristics and quantify the environmental risk thresholds for P leaching. The results showed that the maximum P adsorption capacity (Qmax) initially increased then decreased with cultivation duration. This trend correlated significantly with variations in silt content and calcium carbonate concentration. Both adsorption affinity constant (K) and P buffering capacity (MBC) demonstrated consistent declines with extended cultivation, showing higher values in subsoil than topsoil. Conversely, the P saturation degree (DPS) displayed an inverse relationship with these parameters. Organic matter content and pH emerged as primary influencing factors of soil-phosphate binding capacity through correlation analysis. Environmental risk analysis established critical thresholds for P loss at 68.7 mg/kg (risk threshold) and 335.6 mg/kg (control threshold), based on quantitative relationships between available P, MBC, and DPS. Notably, P leaching risk escalated with cultivation duration, with subsoil showing unignorable P loss risk despite their higher adsorption capacity.