The invention relates to a method for CPU board card program downloading and hardware online detection and a plug-in connector, which is developed mainly aiming at simplifying a series of complex links such as set-up program writing in, hardware circuit detection and application program updating in the actual production and operation process of a CPU board card in the embedded-type system containing an Ethernet interface. The main technical main point lies in the automation and high efficiency of the program downloading and hardware board card test. The technical scheme realizes automatic download of the board card program by using the special circuit design and the flow program and finishes online automatic detection function of a hardware circuit of the board card per se. The CPU board by using the technical scheme can effectively solve or avoid a plurality of problems in the batch production and fully improve the production efficiency and quality of the product.