Two novel carbazole-benzothiazole derivatives 3-((2-benzothiazole-2-yl) ethenyl)-N-ethyl-carbazole and 3, 6-bis ((2-benzothiazole-2-yl) ethenyl)-N-ethyl-carbazole containing carbazole as a donor and benzothiazole as an acceptor were synthesized and characterized by 1H-NMR spectra and UV-Visible spectrophotometer. The compound-doped polyimide thin film with mass fraction 4% were prepared by doctor blading on the glass substrate. The linear and nonlinear optical properties of the thin film were studied using the transmission spectrum method and Z-scan technique with 30 ps pulses at 1 064 nm, respectively. The values of the nonlinear absorption coefficient and nonlinear refractive index of the two thin films were β1=－2.118 9×10－10 cm/W, r1=2.285 2×10－14 cm2/W, β2=－1.275 6×10－9 cm/W, r2=－7.039 9×10－14 cm2/W, respectively. The Z-scan results revealed that the first compound-doped polyimide thin film exhibited reverse saturable absorption and self-focusing effect while the second compound-doped polyimide thin film exhibited reverse saturable absorption and self-defocusing effect.