In tackling key scientific and technological problems on the test stope with a thousand-ton ore for large-diameter longhole mining at Anqing copper mine, a mathematic model for predicting the fragmentation of blasting and its computer program were established to direct the blasting design of stope, improve the blasting result and reduce the mining cost. The calculated results from the model were very conformable to the actual statistic results of the stope and were used to modify the blasting design of the test stope, with a satisfactory result.