The invention relates to a method for preparing
polyol ester lubricating oil by using a composite
solid acid catalyst. The method comprises the following steps of: adding a water carrying agent into
polyol ester and monobasic
fatty acid, performing
esterification reaction under the action of the composite
solid acid catalyst, and dehydrating and esterfying to obtain raw ester; performing filter pressing on the raw ester to separate the raw ester from the
solid acid catalyst, wherein the catalyst can be recycled; and performing reduced pressure
distillation on the raw ester to remove the residual
fatty acid, and then deacidifying and decolorizing to refine with heating by using a refining adsorption
bed layer respectively to obtain low-
acid value polyol ester lubricating oil. The method has the advantages that the catalyst can be recycled, the esterification rate is high, an aftertreatment process is simple, and a product is low in
acid value, high in purity, environment-friendly and suitable to be produced industrially. The reaction esterification rate can reach over 99 percent, and the
acid value of the ester product obtained through refining can be controlled to be less than 0.01mg KOH / g. The product is excellent in visco-temperature performance, high in
lubricity and
thermal stability, strong in hydrolytic stability, low in volatility and excellent in electrical insulation property.