Objective The purpose of this study was to evaluate the maximum binding(Bmax) and affinity(Kd value) changes of acetylcholine receptor (n-AchR) in rat lateral pterygoid muscles after functional mandibule advancement.Methods 40 five-weeks-old male Sprague-Dawley ratswere equally divided into experimental and control group. The mimic functional appli- ances were used in experiment group and the ratswere killed after 1, 3, 7, 14 days. Radio-ligand binding assay (RBA) was ap- plied to determine the maximum binding(Bmax) and Kd value of n-AchR of lateral pterygoid muscle.Results The Bmax of n- AchR in experimental group was higher than that in control group and the Kd value always kept in high level.Conclusion The functional orthopedics can increase the Bmax of n-AchR in rapid growing rat lateral pterygoid muscles.