Based on nickel chromium substrate，a novel electochemical sensor was prepared by coating chitosan on the surface of nanotubes modified ultra thin carbon paste electrode（CTS-CNTs-UTCPE），and this sensor was further employed for electrochemical determination of o-，m- and p-nitrophenol.Electrochemical behaviors of o-，m- and p-nitrophenol on CTS-CNTs-UTCPE were investigated by cyclic voltammetry（CV）and semi-differential voltammetry method.Effects of supporting electrolyte，pH value，onset potential，scan rate and accumulation time on the result of detection were explored.Compared to nickel chromium electrode，ultra thin carbon paste electrode（UTCPE）and carbon nanotubes modified ultra thin carbon paste electrode（CNTs-UTCPE），the new electrode displays a larger oxidative current response to o-，m- and p-nitrophenol in pH 5.72 B-R solution，probably due to the synergistic effects between chitosan and carbon nanotubes.Under the optimum conditions，the presented sensor exhibited wide linear responses to o-nitrophenol ranging from 4.0×10-7mol/L to 8.0×10-5 mol/L with a detection limit（S/N=3）down to 2.3×10-7 mol/L，to m-nitrophenol ranging from 4.0×10-7 mol/L to 8.0×10-5 mol/L，with a detection limit down to 2.9×10-7 mol/L，to p-nitrophenol ranging from 8.0×10-7 to 8.0×10-5 mol/L with a detection limit down to 6.7 ×10-7 mol/L.This presented sensor also showed a good stability and an excellent selectivity，and was successfully applied in the simultaneous determination of o-，m- and p-nitrophenol in artificial water samples.