Taking ultraprecision grinding of silicon nitride ceramic as an example, this paper mostly introduces some influences of diamond wheel’s specialties on the grinding process and surface quality during ELID (electrolytic in-process dressing) grinding of hard and brittle materials. Research indicates that grain size and concentration of abrasive material should be reasonably selected based on the surface roughness. And Inhomogeneity of concentration distribution along wheel circumference will result in heterogeneity of insulator layer state, which will bring difference in the number of abrasive grain in the grinding area, thereby changing the actual cutting depth of every abrasive grain. Dynamic balancing of grinding wheel should be accurately adopted to reduce eccentric mass, furtherly to avoid generating waveness on the workpiece surface. For the purpose of reflecting rightly compositive effect from eccentricity of wheel shape, roundness of the wheel and periodical vibration derived from eccentric mass, actual radial runout of grinding wheel should be well and truly measured and controlled based on the wheel’s surface profile during wheel is rotating at working speed.