Abstract: The methods of multiplication and division were adopted to carry out the multiobjective programming and to determine the objective function so as to optimize stand spatial structure for the total mingling, forest layer index, W_V_Hegyi competition index, uniform angle index, and open degree, taking spatial structure and nonspatial structure as constraints. The model of stand thinning spatial structure optimizing model of Cunninghamia lanceolata ecological forest was built based on the determination of stand spatial structure constraint conditions priority by using grey relation method. This model was then used to determine the optimal solution of stand thinning spatial structure optimization of C. lanceolata ecological forest. The results showed that the stand spatial structure optimization objective function values of C. lanceolata ecological forest followed the order of total mingling (0.7016) > forest layer index (0.7008) > uniform angle index (0.6578) > open degree (0.5960) > W_V_Hegyi competition index (0.5785). Therefore, when considering stand spatial structure constraint condition before stand thinning, we must consider mingling firstly, followed by the forest layer index. The model was used in plots (20 m×30 m), where 14 optimally cutting trees were chosen with a thinning intensity of 14.1%. After thinning, the numbers of diameter class and tree species that describe nonspatial structure remained unchanged; stand mingling was increased by 2.71%, and species spatial isolation level was enhanced; forest layer index was increased by 10.91%, stand vertical hierarchical structure was improved greatly; W_V_Hegyi competition index was reduced by 8.64%, which showed a decline in stand competition pressure; uniform angle index was reduced by 8.25%, which showed a tendency of random distribution in stand spatial structure; open degree increased by 11.98%, which showed an improvement of light transmission. The objective function Q(g) value of stand spatial structure optimization model was increased by 12.18%.