Abstract: Random dot stereograms were used to study the factors of the key problem that existed in the visual comfort of stereo display and was caused by stereo vision comfortable fusion. Subjective behavior experiments were done to analysis the factors to affect CFL(Comfortable fusion limits) of stereo vision by changing the size and shape of a hidden graph, the dots density and dot size in random dot stereograms. Then a prediction model of these factors to CFL was put forward. The results showed that these factors had different influences on CFL under crossed disparity and uncrossed disparity. Under uncrossed disparity, the subjects can stand bigger size of hidden graph, and the perception of fusion limit for the shape is opposite to the perception under crossed disparity. Correlation detection was measured between the prediction values calculated by the prediction model and the measured values. The correlation coefficient achieved 0.998 and 0.977, respectively, under crossed disparity and uncrossed disparity, which indicated that the prediction model could more accurately predict the CFL.