The toughness of abrasive grits means their resistance against breaking under the effect of cutting forces. The commonly used test methods include single crystal static compressing, rolling crushing, mould pressing, as well as milling. In the national standard “GB/T 23538-2009 Conventional Abrasive Testing Methods for Toughness (ball mill method)”, it is stipulated that milling machine is to be used for the abrasive grits F8-F150 to determine their toughness. This method by milling includes testing steps as follows: take a certain amount of abrasive grits , together with steel balls of certain size and certain mass, into the ball milling machine rotating at a certain speed .When the specified total rotations are completed, measure the ratio of the unbroken grits to the total amount of the milled samples. This ratio is defined as the milling toughness of the abrasive grits. In this paper, the milling toughness of different sized black silicon carbide is tested according to the requirement of “GB /T 23538-2009”, and the repeatability of the testing results characterized by test standard deviation is discussed. The test results from different operators using different ball mass are compared and analyzed, and the factors affecting the milling toughness test results are researched. Some suggestions to improve the repeatability of the test results are given.