A planar multi-stage power divider comprises multiple radio frequency transmission lines composed of a metal strap line and a metal plate, wherein the metal strap line of each radio frequency transmission line comprises a lumped input port and K layers of ring strap lines surrounding the lumped input port, the connection between each lumped input port and the corresponding innermost-layer ring strap line and the connection between the ring strap lines are achieved through Y connection strap lines, the outermost-layer ring strap line of each radio frequency transmission line is connected with X output ports through X output strap lines extending outwards, and an isolation resistor is connected between every two adjacent output strap liens through a resistor connection strap line, wherein X is larger than or equal to 3, Y is larger than or equal to 5 and K is larger than or equal to 2. A plane of the power divider has multiple ports and is miniaturized, the flexibility of the X output ports is high, the bandwidth of the power divider is obviously increased through arrangement of the K layers of ring strap lines around each lumped input port, the isolation degree between the ports is good, and the power divider is easy to process and obtain and has good engineering practical value.