Orthometric height i.e., Height above sea level (HASL), it is confined by the earth gravity and is an important geodetic concept, which has been widely applied to the field of economics, military defense, scientific research and son on. For nearly fifty years, concept of normal height has been adopted in China. However, thanks to the rapid development in geodesy and other computation technology, the HASL can be computed as accurately as the normal height. Particularly, the HASL is very fit to the case of wide and high multimountain areas of China. This ideal of orthometric height would be accepted by many people. This study will make a review of three historic periods of the development of HASL theory. The three periods are characterized by (1) definition and approximated evaluation of HASL; (2) proposition of HASL and (3) precise evaluation of HASL. Furthermore, this study also introduces the method of compute on the basic orthometric height level (geoid).