A compound represented by formula I or II and a method for preparing the same. The method includes: a) adding isooctyl mercaptopropionate to a reactor, adding dropwise an aqueous solution of methyltin chloride, stirring and allowing for a complete reaction, and adding aqueous ammonia, an aqueous solution of sodium hydroxide, an aqueous solution of sodium bicarbonate, an aqueous solution of sodium carbonate, or a solution of an organic base to regulate the pH value of a resulting mixture from a starting value of between 2 and 8 to an end value of between 6 and 10 for a primary stage of esterification; and b) allowing a product obtained from step a) to proceed to a secondary stage of the esterification, allowing the product to stand until phases are separated, collecting and washing an organic phase using deionized water, allowing a resulting mixture to stand until phases are separated.