This study aimed to identify the optimal intercropping ratio of sweet sorghum （Sorghum bicolor） and sesbania （Sesbania cannabina） in the Chengdu Plain region and to clarify its effects on forage productivity and interspecific interactions. Five intercropping ratios （3∶1， 2∶1， 1∶1， 1∶2 and 1∶3； sweet sorghum ： sesbania） were established， with monocultures as controls. Agronomic traits， forage yield and nutritional quality were evaluated to assess the overall performance of the intercropping system. The results showed that intercropping significantly reduced plant height and stem diameter of both species. However， the nutritional quality of the mixed forage was significantly improved compared to sweet sorghum monoculture. Crude protein， total digestible nutrients and comprehensive quality indicators increased with the increas of sesbania proportion. Sweet sorghum monoculture produced the highest fresh and dry matter yields， while the 3∶1 intercropping ratio achieved the highest yield among the intercropping treatments. Interspecific interaction analysis indicated a facilitative effect when the sowing ratio exceeded 1∶1， whereas sesbania inhibited sweet sorghum growth at lower ratios. Based on TOPSIS and membership function evaluation， the optimal sowing ratio in the Chengdu Plain was determined to be 2∶1， corresponding to 14.67 kg·hm^-2 of sweet sorghum and 30.00 kg·hm^-2 of sesbania. These findings provide a scientific basis for optimizing the sweet sorghum–sesbania intercropping system in the Chengdu Plain.

Sorghum bicolor  /  Sesbania cannabina  /  Intercropping  /  Production performance  /  Interspecific relationship