This invention relates to an improved structure of USB connector, particularly relating to the structure of USB connector its bottom having a reading slot for memory card. An insulating base having a slice extending from the insulating base, the top of an insulating base and a slice is hollowly equipped with a number of terminal grooves which are arranged every other line for inlaying USB terminals. Mainly the bottom of an insulating base is equipped with grooves whose middle is protrudently equipped with a number of inlaying strips which are arranged every other line, and the rear of the grooves is protrudently equipped with bumps which are corresponding to the inlaying strips. The spaces between each inlaying strip and each bump are provided for inlaying the connecting terminals. In addition, both sides of an insulating base are equipped with inlaying grooves for inlaying a -shape hook which is provided for pressing each connecting terminal not to be loosened. Furthermore, one side of the bottom of an insulting base is protrudently equipped with a guiding slice and inlaying groove for inlaying a top locking spring. Also, a metal shell can fixedly be inserted to an insulating base forming aforementioned a USB connector having upper slot and rear reading slot of memory card.