Abstract: The determination of pump's such-up distance is an important condition to preven t pump from cavitating under the condition of designed flow rate. On the basis of defining pump's suck-up distance, the relations between height of suction, NPSH and suck-up distance are analyzed. The authors summarize the calculation meth ods in the determination of pump's suck-up distance and reduce formulae as well as the problems existed in reference books, give their viewpoint on it.