Abstract: Characteristics of guide bearing are fundamental factors of the vibration characteristics and stability of turbine generator shafts. The properties of guide bearing depend on its geometric parameters and boundary conditions. This paper examines and analyzes the vibration behaviors of a turbine unit shaft to study the influence of different geometric parameters and boundary conditions of the bearing on the characteristics of the shaft, by using the method of single variable parameters and changing the number of bearing tiles, tile clearance, tile angle, and oil film temperature. We obtained the influence trend of guide bearing on the shaft system characteristics via an analysis of the shaft behaviors in terms of critical speed and logarithmic decrement rate. Results show that with the increase in the number of bearing tiles and tile angle or the decrease in oil film temperature, bearing eccentricity gradually decreases and minimum oil film thickness increases gradually, while with the increase in radius clearance, both bearing eccentricity and oil film thickness are increased. Also with the changes in the geometric parameters of the shaft, the first-order critical speed and the logarithmic decrement rate change little, but the second-order critical speed presents a different trend.