Objective : To investigate whether the RW-splint could be used to guide or determine the CR position of the lower jaw so as to provide help for the later diagnostic design. Methods: 20 class ⅡⅠ malocclusion patients were recruited in orthodontic department of Foshan Stomatological Hospital. They were treated by RW-splint for half a year before orthodontic treatment. The overjet of anterior teeth were recorded before and after treatment. Results : The overjet of anterior teeth was (6.792 ± 0.795) mm before treatment and (7.720 ± 0.930) mm after half a year's treatment. The overjet of anterior teeth had significant difference (t=6.319, P <0.01). The overjet change of anterior teeth between before treatment and half year after treatment was (0.928 ± 0.657) mm. Conclusion The RW-splint wearing before treatment can be used to guide or determine the mandible in the CR position.