The invention discloses an automatic rocket tank structure three-dimensional model constructing system which comprises a database, a parameter input module, a parameter storage module, a model dispatching module, a three-dimensional model generating module and a three-dimensional model assembly module, wherein the database is used for storing three-dimensional models of structural members needed for constructing a rocket tank; the parameter input module is used for design parameters which are input by a user to the parameter storage module for storage; the parameter storage module is used for caching the design parameters of the user; the model dispatching module is used for receiving a model dispatching request which is sent by the three-dimensional model generating module, and traversing, retrieve and inquiring a model matched with the request from the database according to the model dispatching request which is sent by the three-dimensional model generating module; the three-dimensional model generating module is used for sending the model dispatching request to the model dispatching module so as to dispatch the corresponding three-dimensional model data in the database; the three-dimensional model assembly module is used for assembling the needed structural members and finishing the construction of the rocket tank three-dimensional model. According to the automatic rocket tank structure three-dimensional model constructing system, the product design efficiency and the product design quality are improved, and the product development period is shortened.