Three-row roller slewing bearings are large and often exposed to quite complex loads. The raceway surface is hardened to improve its carrying capacity. An inadequate hardened raceway depth can cause the raceway to be crushed. In contrast, an excessively large hardened raceway depth can increase the overall vibration, processing difficulty, and cost. Thus, it is critical to determine the optimal hardening depth. We propose a quick method to analyze this depth. The use of non-linear springs instead of a solid roller provides the maximum contact load between the roller and raceway according to the actual load conditions. A finite element model for the local roller and raceway contact is established. The depth thickness under the raceway is divided into a hardened layer, a transition layer, and a core layer. Each layer has distinct elastic–plastic material parameters. The results of a roller and raceway compression experiment validate the roller and raceway finite element model. The accuracy of the raceway as described by the model with different layers is verified by an indentation test of heat-treated 42CrMo. The results show the following: 1) both the value and depth position of the maximum stress increase under normal loads, and 2) the choice of algorithm has a strong influence on the calculated value of the fatigue life.