Hydroxyproline is the main component of collagen,accounting for 20% or so of collagen,and metabolic changes in bone collagen directly affect the level of hydroxyproline in the blood.So inspecting the content of hydroxyproline is very important for pathogenesis and prophylactico-therapeutic measures on osteodystrophy of dairy cows.This experiment monitored and studied the change regularity of serum calcium,serum phosphorus and serum free hydroxyproline of perinatal cow in Hebei Province,and discussed a new and early diagnosis way for osteodystrophy.Thus,effective control measures could be implemented before the bone became deformed without any clinical symptom.The paper provided a theoretical foundation for early diagnosis of perinatal cow.