The flow through a rectangular pocket is described using 2D numerical model and studied by computational fluid dynamics ANSYS fluent 20. It's known that the hydrostatic thrust bearing play a vital role in the design and operation of industrial equipment. The purpose of present work is to study the influence of film thickness change of rectangular hydrostatic pad thrust bearing at constant recess depth of deep and shallow aspect ratios. Numerical simulations of pressure distribution were performed to study the bearing performance under this change. It was clearly established that both for the deep (e/h0 = 100, 152, 233 and 300)and shallow (e/h0 = 2, 4, 8 and 16) aspect ratios the pressure distribution be more stable and uniform with film thickness decreases, while the maximum static pressure be constant. Increasing film thickness values out of standard range can take non uniform pressure distribution.