Two kinds of azo compound host-guest adulterant thin films were prepared, then all-optical poling was made and their second-order nonlinear optical characteristics were studied by UV-visual spectra and second-harmonic generation. The experimental results show that the second-order nonlinear optical coefficient d33of 4′-Nitro-4-dimethylaminoazobenzene was determined to be 6.89×10-1 pm/V, and that of 4′-Iodo-4-dimethylaminoazobenzene is 7.77×10-2 pm/V. In addition, the two kinds of thin films show different second-harmonic generation (SHG) dependence on the thickness and relaxation after saturation. In therory, these phenomena could be explained by that the different substituen result in different molecular dipole property and interaction between azo molecule and host materials.