Abstract: A biodegradable composite film without water solubility was made from chitosan and gellan, glycerin as plasticizers, cross-linked by 4% sodium citrate and 2% calcium chloride. Effect of cross-linking time and pH on the mechanical properties and water resistance of composite film were investigated. Besides, infrared spectrum (FT-IR) , X-ray diffraction (X-RD) , scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize and analyze the structure and thermal stability of the film. The results showed that sodium citrate and calcium chloride cross-linked composite film, and the cross-linking decreased the crystallinity of chitosan and gellan, and then improved thermal stability of composite film. The composite film had the best properties under a cross-linking time of 5min and pH6. 0, tensile strength 91. 45MPa, water solubility 7. 28%, swelling ratio 416. 63%, water vapor permeability 0. 68×10-10g/ (Pa·s·m2) , compounding and ion crosslinking improved mechanical properties and water resistance of single film.