The bending fatigue strength of the tooth is an important index to measure the bearing capacity of the gear. The tooth root transition curve has a great influence on the bending strength of the gear. The profile of the tooth root transition curve depends on the shape of the tooltip. Therefore, the geometry of the tooltip must be considered in the simulation process of tooth profile generation. Contact analysis of helical gears with accurate geometric models is carried out in this paper. After generating tooth profiles machined by tools with different tip radii using MATLAB software, the three-dimensional model of involute helical cylindrical gears is established in CREO, and the stress distribution of gears under diverse load conditions is analyzed by FE software. In the end, it is concluded that the size of the tooltip fillet radius has a great influence on the maximum bending strength of the tooth root, and the strength of the tooth root decreases by increasing the tool tip radius.