Abstract: Aiming at the problem of determining the optimum caving space parameters under 18 m×20 m structural parameters of Meishan Iron Mine，the paper analyzed the mathematical analysis which can optimize the caving space，the morphology of draw body under this structure parameters are simulated by tope dilution drawing experiment，and the morphology features of draw body is adopted to calculate the optimum caving space with the object of difference of recovery and dilution by using the method of getting the minimized.The results show that caving space influences the recovery index evidently，and the caving space of 4.31~5.38 m has more advantage in recovery index.Practice indicates that optimum caving space identified by the mathematical analysis，has a certain directive function in production.

Key words: Caving space, Difference of recovery and dilution, Top dilution drawing, Elliptical drawing body