Abstract: A new way that is thermal assisted high-pressure water jet ultra fine comminuting has been used to comminute the minerals on the experiments.The mineral particles were damaged by thermal shock before they were comminuted finally by high pressure water jet.The experimental results on the ultra fine com- minuting coal,kaolin powder show that the good comminution effect can be gotten making use of the method. When the pressure increases to a certain value,the high comminuting efficiency can be gotten at the first com- minution.The particle size distribution of products by water jet comminuting heat-treated minerals is narrow- er and the particle size is more uniformity than untreated.At the same time,the working pressure of water jet can be reduced lower for the heat treated minerals if the same particle size distribution is gotten.