The mathematical analysis for point-doping in zone melting has been given in detail. A series of general formulae of impurity concentration distribution along the ingot after point-doping zone melting has been derived. In this paper, within the range of our investigation, it is not at difficult, by means of these formulae, to obtain the impurity concentration distribution in an ingot after any number of passages of zone melting, without being restricted by the number of passages of zone melting and the number of doping points.As an example, the impurity concentration distribution after three passages of zone melting for the case of к = 0.35 and four doping points is specifically calculated. It is shown that, if the position and doping amount of each doping point are suitable, for an ingot of 21.5 melting zone lengths, the relative fluctuation of impurity concentration in 16 lengths may be less than ?3.0%.