In order to effectively evaluate the grinding performance of CBN（Cubic Boron Nitride） grinding wheel in the grinding process, a monitoring method of CBN grinding wheel performance was proposed based on Shannon entropy theory and acoustic emission signal. Firstly, the acoustic emission signal of CBN grinding wheel was collected by an acoustic emission sensor. Then, the probability density and distribution of acoustic emission signal of CBN grinding wheel was estimated by using the maximum information entropy. In addition, the characteristics of acoustic emission signals of CBN grinding wheel during cyclic grinding after dressing and residual grinding with different diameters were analyzed and discussed. Subsequently, the relationship between the maximum entropy probability density distribution of acoustic emission signals and the different grinding performance of CBN grinding wheel was established according to the cross entropy principle. Finally, a large number of experiments verified the availability above mentioned estimation method. The CBN grinding wheel wear status and the remaining life of CBN grinding wheel can be monitored.