Synthetic organic heat transfer fluid is a blend of monobenzyl toluene. The product has high purity, suitable kinematic viscosity, low pour point, and good low temperature fluidity; it has good molecular stability and excellent activation performance; it is environmentally friendly. It has good safety and low corrosiveness to equipment; it is suitable for the production process with two alternating heating systems of heating and cooling at the same time. It has a large application space in the fields of pharmaceutical intermediates and liquid crystal industry.