Poly-methyl-methacrylate thin films were deposited by plasma polymerization under different radio-frequency discharge powers, monomer partial pressures, and deposition times. Surface profiler was used to evaluate the thickness and deposition rates of deposited films; Fourier transform infrared spectroscopy for the microstructures; X-ray photoelectron spectroscopy for the surface chemical compositions and atomic force microscope for the surface morphology. In addition to the as-deposited PMMA films, some selected films were further treated by oxygen to modify their surfaces. After thorough material characterizations, the films were used as substrates to culture human hepatocytes for testing their biocompatibility. Results of the cell culture were assessed by trypsin cell count, ELISA and MTT assay. It is found that the human hepatocytes can proliferate and perform urea synthesis well on the deposited poly-methyl-methacrylate thin films with or without oxygen treatment.