Abstract: Grinded gears with hardened tooth flanks have found wide application. However, because of the gear design, tools and particularly the deformation after heat treatment, the involute tooth profile can not be connected smoothly with fillet curve at the root of the toodh. Thus" intersecting edges" or grinding steps with notch" at the root of the tooth often results. Inded this phenomenon exists in the manufacturing practice. In this paper ,using the finite element method on the "grinding steps" of typical tooth form and photo-elastic experiments, this paper analyses and discusses the stress distribution at the "step", propores the concepts of relative fillet coefficient and relative stress concentration coefficint in order to control the stress concentration caused by "steps" and makes such kind of gears to operate reliably under certain conditions. This paper also compares the stress distributions at the "step" with that at the "intersecting edges" and carries out an elementary discussion about how to u9e the gears with "steps".