In order to improve the performances of planar power-combining amplifiers,a power-combining amplifier based on the double-layer planar circuit is designed,which employs a double-layer planar power divider/combiner to improve the integration degree,introduces a right-angle microstrip bend to place the amplifiers and their biasing elements on the sides of the input-output axis to make enough room,and locates the amplifiers on the two sides of the input-output axis for heat dissipation.Afterwards,a four-path power divider and a four-element power-combining amplifier are designed,fabricated and tested.The results show that the proposed power-combining amplifier is of a small-signal gain of 10~16 dB over a wide bandwidth of 2.0~4.5 GHz,a saturated output power of 25.9 dBm at 3 GHz and a power-combining efficiency of 81%.It is thus concluded that the proposed design method is feasible.