Determination of the metastable zone width (MSZW) is of great importance in L-arabinose crystallization, yet it has not been reported before. In this study, the use of an automated temperature logging device (ATLD) to monitor the nucleation temperature (Tm) of L-arabinose in an aqueous solution was demonstrated. Direct comparison with focused beam reflectance measurements (FBRM) confirmed that the Tm determined by the ATLD was reliable. A multiple linear regression model of the Tm and a set of exploratory factors indicated that the Tm was affected by the solution concentration and stirring rate but not the cooling rate. The MSZW of L-arabinose in an aqueous solution was not constant, but ranged from 27.36 to 31.55 ℃.The addition of 2% and 4% impurities (sodium chloride, galactose, glucose, and xylose) decreased the MSZW of L-arabinose. This study offers new opportunity for the use of ATLD as simple, inexpensive, and convenient alternative tool in crystallization monitoring.