A new biosensor for urea based on immobilized Corynebacterium glutamicum 629,coupling with potentiometric amrnonia gassensing electrode, was designed and constructed.The calibration plot of mV measurement vs. logarithmic urea concentration was linear in the range 1.1×10^-4～1.4 ×10^-2mol/L,with slope 51.2 mV/decade in pH 8.0,0.1 mol/L phosphate buffer at 30℃.The relationship between the initial response velocity and the substrate concentration was also discussed.The results indicate that the kinetic response process of the reaction catalyzed by bacterium is similar to one by isolated enzyme. By using Eadie-Hofstee plot,the apparent Michaelis-constant (K_m) and the maxium initial response velocity v_m for urease in the immobilized bacteria membrane were determined. The biosensor was relatively stable for 45 days.