L-Hydroxyproline(Hyp) is a typical amino acid in hydrolyzed animal protein,which is a non-edible substance illegally added in food especially in milk and milk products.Therefore,Hyp could be used as an important indicator for food adulteration of animal protein hydrolysates.It is important for food safety and quality monitoring to develop a fast,efficient and sensitive method for hydroxyproline detection.This article reviewed the extraction,cleanup,derivation and determination methods of L-hydroxyproline in foods and biological samples.