The stand structure diversity of Cunninghamia lanceolata forest was comprehensively evaluated, in order to provide the theoretical basis for improving the stand structure diversity and accurately formulating forest management measures. Taking the Cunninghamia lanceolata forest in Fushou experimental forest farm of Pingjiang county, Hunan Province as the research object, the stand spatial structure unit was constructed by four adjacent trees. Nine indexes were selected, including complete mingling degree,Simpson diversity index and Shannon-Wiener index in characterizing the stand tree species composition diversity, size coefficient of variation, mean size differentiation index and angle competition index in characterizing the tree size differentiation diversity, and uniform angle index, storey index and spatial density index in characterizing the tree spatial distribution diversity, to construct a structural equation model for the evaluation of stand structure diversity and determine the weight of each index for a comprehensive evaluation of stand structure diversity. The results showed that:(1) For the structural equation model of stand structure diversity evaluation, the Chi-square degree of freedom (χ²/df) was 1.409, which was between 1-3. The values of CFI, NFI, TLI and GFI were 0.985, 0.953, 0.978 and 0.931, which were greater than 0.9, respectively, and the RMSEA was 0.048, which was less than 0.05. All indexes were well fitted, the fitness of the model was good, and the research requirements were satisfied. (2) The weights of the three endogenous latent variables stand tree species composition diversity, tree size differentiation diversity and tree spatial distribution diversity were 0.3518, 0.3201 and 0.3281, respectively, with approximately the same effect on the exogenous latent variable stand structure diversity. The Shannon-Wiener index was the key factor affecting the stand tree species composition diversity. Angle competition index was the key factor affecting the tree size differentiation diversity. The storey index was the most important factor affecting the tree spatial distribution diversity. (3) The comprehensive scores of the stand structure diversity of Cunninghamia lanceolata forests in the three age groups in the study area were 0.3364, 0.4396 and 0.4588, respectively, which were evaluated in the grade Ⅱ and Ⅲ. The stand structure diversity was low and did not reach the ideal state. In this paper, the evaluation results objectively characterized the current status of the stand structure diversity of Cunninghamia lanceolata forest in the study area, showing that it was scientific and feasible to apply the structural equation model to evaluate the stand structure diversity, it is hoped to provide a new idea for the evaluation of the stand structure diversity.