A wave choke system for an oven door of a microwave oven has an elongated channel for an outer portion of the oven door and an elongated cover sheet covering partially the width of an open longitudinal side of the channel. The cover sheet includes a plurality of slots extending perpendicular to the longitudinal axis of the cover sheet. Each slot includes an open end at a longitudinal edge of the cover sheet and a closed end on the opposite side of the open end, a broadening in a central portion of the slot, a first small portion between the open end and the broadening and a second small portion between the broadening and the closed end. The slots are reciprocally intersected, so that the contours of the slots and the intermediate pieces between the slots are formed complementarily to each other.