The purpose of this paper is to find a method to study the lubrication character of the main bearings and load condition of the crankshaft about the marine two-stroke diesel engine. Based on the finite element method, multi-body dynamics, elastohydrodynamic and Green-Tripp theory about contact, the simulation of coupling between the elastic crankshaft and engine block is carried out. The load of main bearings, the minimum of oil film thick, orbital path of journal, average of asperity contact pressure are explored. The results indicate that the lubrication is good except No.2 main bearing. Parts of main bearings appear three peaks in a working cycle, which shows that above theory and elastic crankshaft and engine block is obligatory to simulate the lubrication and load condition accurately.