The invention relates to a method for purifying hydrogen from a hydrogen rich gas by using a pressure swing adsorption method. The method comprises the processes of adsorption, first uniform decompression, second uniform decompression, third uniform decompression, fourth uniform decompression, reverse release, washing, fourth uniform boosting, suspending, third uniform boosting, second uniform boosting, first uniform boosting and boosting of a product gas. Through the processes, the hydrogen in the hydrogen rich gas is purified, and the product hydrogen of which the purity is greater than 99.99% is obtained, so that complete regeneration of an adsorption tower is achieved and the method is energy-saving, environment-friendly and good in stability.