A straight fin for a device for recovering the waste heat of raw coke oven gas in the ascension pipe of the coke oven includes the straight fin body and a group of V-shaped notches disposed on the straight fin body. The depth h of the V-shaped notches is less than the width H of the straight fin body. The distances between the adjacent V-shaped notches increase from bottom to top in the longitudinal direction of the straight fin body. The present invention further provides a heat recovering device and a power generation device both including the straight fins. Moreover, the width, the angle, and the distances in the longitudinal direction of the V-shaped notches at the top of the straight fin are determined according to the temperature field distribution during use of the device.