This paper presents the result of researching, calculating fluid thin film bearing that is type of thrust bearing uses for vertical rolling grinding machine. Based on Monte-Carlo simulation, used DE (Differential Evolution) algorithm in order to calculate some nondimensional coefficients to determine optimal geometric parameters of segment into fluid thin film bearing so that fluid goes through slot with minimum pumping capacity. This result's applied for calculating of fluid thin film bearing that is type of thrust bearing is used for vertical rolling grinding machine with capacity at 15 tons/hr - Product of National Project "Research calculating, designing and machining process fluid thin film bearing with load at 80 tons" with KC.05.18/06-10 Code.