It is a very important procedure to establish the occlusal plane in the construction of complete denture. So many methods have been utilized to establish the occlusal plane in complete denture prosthodontics. However, no single method seems to fully accepted. This study was aimed to review the literature on establishing the occlusal plane in complete denture prosthodontics, to measure the distance from the lower border of the upper lip to the upper incisal edge and to investigate the correlation between the ala-tragus line and the occlusal plane. The results ware as follows ; 1. The average distance between the lower border of the upper lip and the upper incisal edge was $1.45{pm}1.28mm$. 2. The distance between the lower border of the upper lip and the upper incisal edge had a tendency to decrease with age. 3. A angle of the ala-tragus line to the occlusal plane measured with Fox plane was $-1.41{pm}2.33^{circ}$. 4. The ala-tragus line to occlusal plane was nearly parallel, cosidering curve of spee in the upper natural teeth.