Abstract: For heat dissipation of the high power solid state laser (HPSSL), a spray cooling system based on refrigerant cycle was designed, and its heat transfer performance was studied. Because the compressor in the refrigerant system needs lubricating, it is inevitable to mix the lubricating oil in the coolant. Lubricating oil has influence on the viscosity, surface tension of the coolant, and may produce oil film, which could strengthen or inhibit the heat transfer process of the coolant. We analyzed the influence of lubricating oil on spray cooling heat transfer performance. The experimental results show that lubricating oil increases the resistance of coolant passing through the nozzle and decreases the coolant flowrate, but as to this system, this influence could be neglected. Lubricating oil enhances the heat transfer performance of coolant, and benefits uniform distribution of the heat source temperature at low heat flux. Lubricating oil also enhances the critical heat flux and heat dissipation ability of the system, making this spray cooling system more beneficial to HPSSL heat dissipation.