Recently, there is an increasing interest in the molecular beam epitaxy growth of various high quality heterostructures on the nonpolar GaAs(110) surface for the unique properties which arise from this unconventional orientation. Considering that the Ga and As atoms are coplanar in GaAs(110) surface, the range of bestgrowth temperature is small. It is difficult to find the best growth condition by observing the change of reflection high energy electron diffraction (RHEED) pattern because this kind of (1×1) RHEED pattern is insensitive to growth temperature and V/III beam equivalent pressure ratio. In the process of the GaAs(110) quantum well growth, we observed the single and double period variation of oscillation of RHEED intensity. This implies that there are two growth modes (monolayer-by-monolayer and bilayer-by-bilayer) of GaAs quantum wells growing on the GaAs (110) substrate under different growth conditions. The measurements of transmission electron microscopy and photoluminescence at room temperature showed that the quantum wells have very bad optical property under the bilayer_by_bilayer growth mode, while the quantum wells grown under the monolayer-by-monolayer growthmode have much better optical property with rough interfaces. By means of RHEEDoscillations, high quality quantum wells have been grown on GaAs (110) substrate under optimized growth conditions.