For the purpose of higher electro-optic (EO) coefficients, the double EO molecules polymer thin film devices are prepared by mixing a small nonlinear optical (NLO) into the host polymer. The EO coefficients are tested after the poling process. The effect on the EO coefficients by the different mixing proportion and different poling temperature are analyzed in details. The EO coefficient increases as the mixing proportion becomes larger, but decreases while the mixing proportion is too high. The reason is that the glass transition temperature falls dramatically with a high mixing proportion, which leads to the phase separation during the poling process. The test of the sample orientation stability with a suitable mixing proportion is performed. Experimental results show that the double EO molecular polymer thin film possess a considerable EO coefficient after being placed for a long time, although the dielectric relaxation phenomenon still exists.