The LS—SVM (least square supporting vector machine) model of combined tar removal process in pine block gasification was established according to the experimental data. On the basis of condition optimizing for tar removal in the furnace, multi-objective optimization function for catalytic activity was put forward, and then the Pareto-optimal solutions were gained after optimization. The results showed that the tar content from gasifier outlet was less than 2g/m3, which met the requirements of inlet tar content for catalytic cracker. The tar content at the entrance of tar catalytic cracker was between 0.126g/m3 and 0.340g/m3.The gas heating value was more than 4MJ/m3, met the engineering requirements, so after condition optimization, the gas quality is better than that of the experimental results.