Abstract: Currently, pharmaceutical research and development is becoming increasingly diverse. Modified new drugs, as an important sector, demonstrate significant advantages in enhancing drug efficacy, shortening development timelines, and increasing market competitiveness. This paper reviews the current status and development trends of long-acting injections in the field of modified new drug research and development. It systematically explores formulation development strategies for long-acting injections, covering various dosage forms including oil-based long-acting injections, injectable suspensions, microspheres, liposomes, and in-situ gels. The aim is to provide scientific basis and references for the improvement and innovation of long-acting injections.