The bushing of connecting rod small end is one of the most prone components to failure in diesel engines. According to previous study, the oil flowrate and storage of small end bearing with splash lubrication are both minimal at maximum speed. Thus the optimization of oil bores was performed using a model based on smooth particle hydrodynamics. By adjusting the angle between the axes of two oil bores to 90°, the oil flowrate and storage increase from 0.036 mL/s and 0.04 mL to 0.094 mL/s and 0.045 mL, respectively. A semicolumn baffle above oil bore away from piston cooling nozzle further increases them to 3.564 mL/s and 0.8 mL. The optimization greatly enhances the cooling intensity and oil supply stability of small end bearing, conducing to prevent bushing failures.