Urease was doped into polypyrrole (PPy) film when pyrrole (Py) was polymerized by cyclic voltammogram. By Combination of PPy modified urease electrode and CO2 gas-sensitive electrode a bioelectrochemical sensor was formed
which responses to urea. Factors affecting the activity of urease in PPy film were studied and activation energy of the ferment was determined. It was found that electrode potential is in direct proportion to the logarithm of the concentration of urea within the concentration range of 5.0×10-5~1.0×10-2mol/L.