Abstract: Based on analysing the factors influncing loosener efficiency, this paper points out that the operat ing parameters of loosener are an important factor and it must be determinated rationally; suggests using fragmental efficiency as an evaluation index of rational operating parameters, Combining the practice of rock loosing in Xiaoyi Aluminum Mine, this paper introduces using the field test and analytical calculation method for determinating the rational operating parameters, and suggests a formula calculating the splitting force.