The embodiment of the invention provides an advertisement putting method and system. The target population is preloaded in the form of categories, and advertisements are put in real time according to an index from users to categories and an index from the categories to target units. The advertisement putting method comprises the steps of creating an advertisement unit, specifying a commodity code associated with the advertisement unit, and mapping the commodity code into a category; generating a target population corresponding to the category, and pre-loading the target population of each category to the index from users to categories; generating an index from categories to advertisement units according to the commodity code associated with the advertisement unit and the category mapped by the commodity code; acquiring and analyzing user information, finding a category corresponding the user according to information acquired by analysis and the index from users to categories, then finding an advertisement unit corresponding to the category according to the index from categories to advertisement units, and playing the advertisement unit.