Abstract: Thermohydrodynamic calculation and analysis for main journal bearings in multi-cylinders ICE were made, which indicates that besides design parameters, practical complications also have influence on lubrication condition of main journal bearings. By means of calculation and analysis for orbital paths and minimum oil film thickness(MOFT) of main bearings, it was discovered that some factors, such as overload, big radial clearance between pin and wall, overheat and loading with cold machine of multi-cylinders ICE can make against oil film formation of lubricant, quickly produce friction and wear.