The power division network is one of the key components of high power microwave (HPM) phased array antenna. It is used to divide HPM into several paths and feed them into phase shifter and element antenna. In such a network, the over-mode circular waveguide to multi-channel rectangular waveguide power divider has the function of mode conversion and power distribution. It is the front end of the power division network and requires high power handling capability, high transmission efficiency and low reflection. In this paper, the design, simulation, fabrication, and small signal test of the power divider from Ku-band GW-level over-mode circular waveguide to 8-channel rectangular waveguide were carried out. Subsequently, the power handling capacity of the power divider was evaluated utilizing the established power capacity testing facility. The experimental outcomes demonstrated that within the frequency band of 14.7 GHz±200 MHz, the reflection coefficient was consistently below -20 dB, the transmission coefficient exceeded -9.1 dB, the port imbalance was maintained at less the 0.4 dB, and the power handling capacity exceeded 900 MW.