Using pig collagen and titanium sulfate as raw material，by tanning reaction with high temperature calcination，the nanometer titanium dioxide was prepared.Then，fixing the nanometer titanium dioxide-chitosan（Cs） nanocomposites on gold electrodes through electrostatic adsorption，using abundant amino in Cs to absorb gold nano particles and lastly absorb alpha-fetoprotein antibodies,an AFP immunosensor was successfully fabricated.The techniques of UV-vis spectroscopy(UV-Vis)，infrared spectroscopy(FT-IR)，X ray diffraction(XRD) and transmission electron microscopy were used to characterize the nanometer titanium dioxide.Under the optimal conditions，the immune sensor showed a good linear relationship for AFP in the range of 0.01-100 ng/mL，with a correlation coefficient of 0.998 2 and a detection limit of 0.003 ng/mL.