Thinning is an important part of forest stand management which removes unhealthy and undesirable trees, benefiting the remaining trees. Selecting the trees to thin presents quantification and spatial distribution challenges for stand managers. In this study we created a model to guide thinning operations, named Stand Uniform Index (SUI). Managers can use this model to quickly choose the trees to remove in the planning of thinning operations. Our study discovered that Stand Uniform Index is affected by diameter at breast height (DBH) and the distances between trees. When DBH was a constant value, distances progressively rose from 1 to 5 m and the index ranged from 0.5690 to 2.8452. When the distances were constant, and DBH varied greatly from 10 to 50 cm among trees, the index varied from 0.5690 to 0.1188. This indicated that trees were concentrated in a sampling area where the Stand Uniform Index was great. The Stand Uniform Index resolved the problem of quantification and spatial distribution modeling for thinning operations. Simulation of thinning operations using this index provides the manager with better understanding of a stand to make thinning decisions. This study showed that using the Stand Uniform Index can assist with forest management policy and improve thinning operations.