Abstract: This article analysed the main reasons which made the lotus root broken by the lotus root digger; offered the rate of lotus root broken to evaluate the quality working of the digger.After investigating the geometry, distributed regular pattern of wild lotus root at the Hong Lake District in Hu Bei Province, and analysing of statistics as well as the concept of math abstract, then set up a math model for the rate of lotus root broken in qhe digger, tnd analysed the influening reasons of rate of that.