In-situ forming polymeric formulations drug delivery systems is in sol form before administration in the body, but once administered, undergoes gelation in-situ to form a gel, from which drug gets released in sustained and controlled manner. The formulation of gel depends upon factors like temperature modulation, pH changes, presence of ions and ultra-violet irradiation. The objective of this study was to develop a novel in- situ gel system for sustained drug delivery of Alfuzocin using natural biodegradable polymers. The system utilizes polymers that exhibit sol-to-gel phase transition due to change in specific physico-chemical parameters. In-situ gel was formed at a biological pH. Gellan gum used as a polymer and CaCO3 was used as a cross-linking agent. In vitro release studies were conducted in 0.1 N HCl and cumulative amount of drug release was analyzed by spectrophotometry. From designed set of experiments, it was evident that formulation containing Gellan gum control the release of drug for longer duration. The in-situ gel exhibited the expected viscosity, drug content, pH, in vitro gelling capacity, in vitro floating ability and sustained drug release. The stability studies were carried out for 3 month.