The invention discloses a method for preparing lactic acid through catalytic hydrolysis of isoamyl lactate. According to the method, isoamyl lactate and water are adopted as raw materials, an ion exchange resin is adopted as a catalyst, lactic acid is prepared through a hydrolysis reaction, and by controlling reaction process conditions, lactic acid of a high yield is prepared with low cost. The method disclosed by the invention has the advantages of being rapid in hydrolysis reaction, high in isoamyl lactate conversion rate, mild in reaction condition, easy in catalyst recycling, and the like.