The actual engine (especially vehicle engine) does not always operate under rated operating condition and its operating condition changes constantly. However, only the lubrication performance of crankshaft bearing at rated engine operating condition has been generally analyzed in current design and research of engine crankshaft bearing. In this paper, a four-stroke four-cylinder engine is taken as the studying object, the load and lubrication of crankshaft bearing under different operating conditions are analyzed systematically and comprehensively. The load of connecting-rod bearing is calculated by the dynamic calculation method, the loads of all crankshaft main bearings are calculated by the whole crankshaft solid-element finite element method, and the lubrication performance of crankshaft bearings are analyzed by the dynamic method. The results show that there are major differences in the changes and numerical value at corresponding moment of the loads and lubrication performance of crankshaft bearings in an engine operating cycle under different engine operating conditions; the most unfavorable case of the lubrication performance of crankshaft bearings may not take place in the rated engine operating condition. There are also major differences between the lubrication performance of connecting-rod bearing and that of main bearing and between the lubrication performances of main bearings one another. Therefore, it will not be reasonable that the lubrication performance of a certain crankshaft bearing (connecting-rod bearing or one main bearing) is analyzed in the design of engine crankshaft bearing. It is necessary to analyze simultaneously the lubrication performances of all crankshaft bearings under different engine operating conditions.