There are three typical coking coal elected in order to research transformation characteristics of the sulfur in coking coal in the process of washing and pyrolysis.At first stage,the migration law of sulfur in washing process is studied.At second stage,the migration of total sulfur,pyrite sulfur,sulfate sulfur and organic sulfur in clean coal in pyrolysis process was studied by the experiment of 1 kg test oven.As a result,pyrite sulfur in raw coal is mainly removed during coal washing.In the process of pyrolysis,pyrite sulfur removal is essential to the reaction when temperature is below 700 ℃,but organic sulfur removal plays key role when temperature is above 700 ℃.In addition,there occurs a chemical phenomenon that pyrite sulfur and fatty sulfide are converted to thiophene sulfur in the high temperature region.