This article mainly discusses the concept and harm of the incomplete slag melting in the blowing process and analyses its causes. Then it introduces the corrective measures adopted by Laiwu Steel Plant to solve the prob- lem. By optimizing the slagging process， lance control and slag splashing process， the consumption of ferric charge and refractory are all decreased， on the contrary the working life of oxygen lance is raised. It proved that these measures not only meet the market trend but also reduce the production costs.