The main bearing of the shield machine is characterized by large size,high load and slow speed.Studying the lubrication condition in the main bearing cavity of the shield machine is crucial to ensure the reliability of the main bearing of the shield machine.The three-dimensional modeling software and fluid simulation software were used to model the main bearing of shield machine and simulate the fluid domain in the cavity.The influences of main lubrication parameters on the lubrication state in the cavity,including the position distribution of oil inlet,the selection of oil inlet and lubricating oil viscosity,were studied.The relationship between lubrication state and temperature in the cavity was analyzed.The results show that the position distribution of oil inlet has a great influence on the lubrication state,and the asymmetric oil inlet distribution is more favorable for the main bearing of shield machine with extremely low speed rotation and heavy load.To improve the lubrication state,the oil inlet should be divided into the main oil inlet and the auxiliary oil inlet.The main oil inlet should be kept normally open,and the opening of the auxiliary oil inlet depends on the working condition.The viscosity of lubricating oil has a great influence on the lubrication state and temperature.There is an optimal viscosity range to maintain a low temperature and good lubrication condition.The volume fraction of lubricating oil at the corresponding position is inversely proportional to the temperature.