Hydrostatic journal bearings are recommended for supporting shafts operating at high speeds and under heavy loads in the industry. In the journal bearings, lubricant viscosity decreases with increasing temperature at high rotation speeds and hence, the fluid between the surfaces should be circulated using a pump to cool the lubricant. However, the lubricant supplying between the surfaces at the high flow rate causes the whirl instability and vibrations problems in the bearing-shaft system. These instability problems give rise to significant damage on the system during operating at the high speeds and under heavy loads. As a solution to this problem, it could be suggested to control the variation of the lubricant viscosity concerning the temperature by adding nanoparticle. In the present work, the effects of the lubricant with nanoparticle additives on the load carrying capacity of a hydrostatic journal bearing are theoretically investigated. The fluid film flow between the bearing and rotor surfaces are modelled with Reynolds equation and the viscosity term in Reynold’s equation is defined as a function which depends on the nanoparticle properties. Then, the pressure distribution is obtained with solving the film flow equation and the load capacity is calculated for different nanoparticle parameters using this pressure distribution. The results show that the usage of the lubricant with nanoparticle increases the load performance of the hydrostatic journal bearing and the influences of the nanoparticle size on the load performance is more dominant for high volumetric ratio.