The cold water-soluble gel agent was screened and the gel medium composition and developer concentration were optimized，by comparing with colony count test results between bacterial testing slip and pour-plate culture method. The best composition was that carrageenan and CMC mixed in 21 (W/W), the gel powder and the medium powder mixed in 21 (W/W) and TTC actual concentration of 0.025 mg/mL. The colony count test results were no significant difference compared with the pour-plate culture method. The optimized gelling agent and color developer could be used to prepare bacterial testing slip.