Abstract: In order to meet the demand for the miniaturized microwave sources, a new kind of miniaturized permanent magnetic focused multi-beam klystron with output power of 10 MW at L-band is designed and developed. In this paper, the brief design process and the test results of the klystron are presented. The klystron adopts the method of periodic reverse permanent magnetic focusing combined with multi-beam fundamental-mode cavities, which achieves a peak output power of more than 10 MW under the cathode voltage of 70 kV, with an efficiency of more than 45% and a gain of more than 46 dB. The weight of the klystron is only 76 kg, which reduced the weight of L-band 10 MW class peak power klystron by an order of magnitude compared with the conventional klystrons.