【Objective】This study investigates the effects of competition on the stem taper of Larix olgensis by incorporating competition indices into a taper equation，thereby developing a competition-inclusive taper model to provide a theoretical foundation for the silvicultural management of L. olgensis plantations.【Method】Data were collected from L. olgensis plantations in Dongfeng County，Jilin Province，China. The modified Kozak（2004）variable-exponent taper equation served as the base model. Plots were treated as grouping variables，and nonlinear mixed-effects models with various parameter combinations were fitted. Model performance was assessed using Akaike’s Information Criterion（AIC），Bayesian Information Criterion（BIC），and log-likelihood values. Likelihood ratio tests were applied to compare models and identify the optimal plot-level mixed-effects parameters. These optimal parameters were subsequently expressed as linear functions of competition indices to formulate a generalized taper equation incorporating competition effects. The generalized taper equation was used to simulate stem profile variations under differing competition intensities.【Result】（1）Models with a single mixed-effects parameter exhibited the highest fitting precision； adding further mixed parameters did not substantially enhance model accuracy.（2）Stepwise variable selection identified the optimal competition indices as I_c5（Hegyi competition index），I_c6（neighborhood comparison），I_c7（average diameter of competing trees），and I_c8（average distance of competing trees），with the Hegyi competition index exerting the strongest influence on stem taper.（3）The generalized taper equation outperformed the base model in terms of fitting accuracy.（4）Simulations of stem profiles revealed that competition significantly influences the stem form of L. olgensis. As competition intensity increased，stem taper progressively increased，with large-diameter trees demonstrating greater sensitivity to competition variations.【Conclusion】In the management of L. olgensis plantations，particularly for stands oriented toward large-diameter timber production，selective cutting should be conducted timely to remove competing trees within the competitive neighborhood of target trees. This silvicultural intervention can effectively regulate inter-tree competition dynamics，alleviate the competitive stress exerted on target trees，and consequently facilitate their growth and development.