The present invention relates to a link system and link method of an upper shopping mall and an independent shopping mall of API (application programming interface) link method, in particular, to a technology that builds and manages an independent shopping mall having an independent domain address and an user interface besides the upper shopping mall which is registered together with the other sellers. According to the present invention, provided is a link system of an upper shopping mall having a plurality of sellers and an independent shopping mall operated independently by one person among the sellers, of API link method, which comprises a shopping mall database that stores a goods information, a member information, and a payment and delivery information; an independent shopping mall web server receives a goods inquiry or a purchase request from a user to output a factor for extracting data of the shopping mall database, and receives a necessary data from the shopping mall database; and an API server receives a factor from the independent shopping mall web server to analyze, and accesses to the shopping mall database so as to request that the necessary data should be sent to the independent shopping mall web server.