Corosolic acid (CA) has become one of the most popular natural compounds in recent years because of its insulin-like and anti-cancer activities. In present study, a simple, precise and accurate high performance liquid chromatography method was developed to determine CA in Psidium guajava. An Agilent SB-C18 (4.6 × 250 mm, 5 μm) column was used for separation and analysis. The separation was performed with a constant mobile phase of acetonitrile and 0.2% formic acid in water (75:25) at a flow rate of 1 min/ml. The analytes were detected at the wavelength of 210 nm. The method was validated in terms of calibration curve, sensitivity, precision, accuracy and stability, and was applied to determine CA in leaves and fruits of P. guajava from different locations. The results showed that CA was detected in leaves with the content almost 1%, but not detectable in fruits of P. guajava. After the leaves were hydrolyzed with hydrochloric acid, the content of CA in leaf samples significantly increased up to 1.54%, and the increasing rates were more than 48.6%, suggesting that the leaf of P. guajava is a potential resource rich in CA, and hydrochloric acid hydrolysis might be a cost-effective approach to produce CA from the leaf of P. guajava.