The invention relates to a millimeter wave active antenna unit and an inter-PCB (Printed Circuit Board) interconnection structure. The inter-PCB interconnection structure comprises a main board and anAIP (Antenna in package) antenna module. The main board is a first multilayer PCB and provided with a signal transmission line and a first pad electrically connected with the signal transmission line. The AIP antenna module is a second multilayer PCB and provided with a second pad, an impedance matching transmission branch, an impedance line and a signal processing circuit. The main board and theAIP antenna module adopts a mode of direct welding interconnection between the multilayer PCBs, thereby saving an expensive millimeter wave interconnection assembly on the one hand, and thus being very low in cost; On the other hand, the mode of direct welding between the boards improves the reliability of the product, the interconnection design between the multilayer PCBs can be realized, and the integration between the multilayer PCBs is greatly improved, thereby being conducive to the miniaturization design of millimeter wave equipment. In addition, the second pad and the signal processingcircuit are provided with the impedance matching transformation branch and the impedance line therebetween, thereby being suitable for a wider frequency range and a wider lamination number range.