Polymer/multiple walled carbon nanotube (MWNT) thin films on glass slide substrates have been fabricated by using the spin-coating method. The optical power limiting performance and nonlinear absorption in these films have been characterized experimentally. Transmission electron micrograph and scanning electron microscope (SEM) techniques have been used to investigate the interaction between polymer molecules and MWNTs. SEM images of polymer functionalized carbon nanotubes show that polymer molecules and MWNTs can interact via -stacking to increase solubilization of MWNTs, which can be used to explain the optical power limiting effect. For quantitative comparison of different polymer MWNT thin film performance, the open Z-scan technique is employed to measure nonlinear absorption coefficient and optical power limiting effects of different polymer MWNT thin films.