This study was aimed to investigate the effect of the differential lock on the drive wheel slip and fuel consumption rates for the three tractors (ITM??? ?WD-ITM??? ?WD-ITM??? ?WD). In this research, the factors were tillage depth at two levels (?? and ?? cm) and differential lock (engaged and not engaged). The experiments were carried out based on factorial experiment in randomized complete block design with three replications separately for each tractor. The experiments were conducted in the same conditions with appropriate soil sitaution at the research field of Shahrekord University. Analysis of factors effects were obtained by measuring the parameters of drive wheels slip, fuel consumption of the tractor and the travelling time. The results showed that the use of differential lock during moldboard plow for all tractors caused to reduce the fuel consumption and the route travel time. The use of differential lock had significant effect on the driving wheel slip of tractor, in such a way by using of differential lock, the average of rear right wheel slip and the rear left wheel slip reduced as ??.?? %and ??.?? respectively. Also, with increasing in plowing depth the driving wheels slip, fuel consumption and the rout travel for all tractors increased in two situations of differential lock.