The invention discloses petroleum sulfonate and a preparation method thereof. The petroleum sulfonate comprises a petroleum component, a catalyst, an alkali solution, hydrogen and sulfur trioxide. Thepreparation method of the petroleum sulfonate includes preparing a sulfonated raw material; performing primary sulfonation and extraction to obtain unsulfonated oil and an extracting agent containingpetroleum sulfonic acid; repeating sulfonation and extraction on the unsulfonated oil until no unsulfonated oil is obtained; combining and distilling the extracting agent containing the petroleum sulfonic acid to obtain the petroleum sulfonic acid; performing ageing and neutralizing to obtain a petroleum sulfonate solution, and concentrating and drying the petroleum sulfonate solution to obtain apetroleum sulfonate product. The petroleum sulfonate product has high good interfacial tension performance, a sulfonation reactor has less coking during preparation and long operating cycle, and thecost is reduced.