The assembly of con rod bearing and crankpin is a key friction pair which offers an important guarantee for stable operation of diesel engine. Specific to the non-road 2-cylinder diesel engine developed independently and based on the theory of thermoelastohydrodynamic lubrication as well as multi-body dynamics, this paper establishes a multi-body dynamics model for con rod big end bearings of the 2D25 horizontal diesel engine and makes a research on the influence of bearing width, bearing clearance, and oil inlet position and diameter upon lubrication of con rod bearing, taking into consideration that of the surface appearance of bearing bush and the elastic deformation of bearing bush and axle journal upon the same. Research results show that bearing width and bearing clearance are the major factors that influence lubrication characteristics of con rod bearing while oil inlet position and diameter only have a small influence on such characteristics. An optimization scheme for con rod bearing is selected through orthogonal test: bearing clearance of 0.042mm, bearing width of 33mm, oil inlet position of 285° and oil inlet diameter of φ7mm. After optimization, the minimum oil film thickness is remarkably increased by 43.72% while the average total frictional power consumption and peak oil film pressure show very little change compared to the original scheme.