Abstract: The design of election beam collector for high-power microwave source driven by sheet electron beam is presented. Besides collecting electrons, the collector can effectively transform rectangular TM11 mode engendered by microwave source with sheet electron beam. The transmittal efficiency is higher than 95% when the frequency is in the range of 13 GHz to 27 GHz. The wide-band character can improve efficiency of the design and simulation of high-power microwave source with sheet beam. The transmittal efficiency of TM11 mode is not sensitive to the thickness and length of the collector. The heat dissipation of this collector performs well and it is able to hold the impact of electron beam with 3 kA, 300 kV, 30 ns pulse-width and 50 Hz repetitive operation, just cooled by natural air convection and heat radiation. The results are important to the design of high-power microwave generators driven by sheet electron beams.