This article sets out the distinction between Red hardness and thermal rigid these two definitions and discusses thermal rigid differences between diamond tool matrix and high-speed tool steel.The Author figured out that it is right the thermal rigid affects the performance of the diamond tool matrix but not the red hardness.Only the hardness of the matrix cannot be the evidence of its wear resistances.Thermal rigid occurred at high temperature is the main factor to effect matrix wear resistances and diamond-wrapped inlay ability.As research and recognition goes on,thermal rigid of matrix has great hope to be taken as the main functional specification of diamond tools powder matrix.