A treadmill with a preferred frame relates to a running track frame being anchored at the two sides of the mainframe that primarily used for accommodating and stabilizing a running board. And the front and the back of the running board is coordinated with front and rear rollers, and combined with a running track to provide the user to stand on top of the running track to perform the jogging motion. At this time, the running track will start to rotate repeatedly around the perimeter of the front and rear rollers due to abrasion. The characteristic is the particular runner frame has at least one opening slot, or equipped with an open slot on one of the surfaces, while the total length of that open slots shall exceed one-half of the distance between the front and rear rollers as an optimal choice. Therefore, the existence of that opening slot is utilized to provide adequate reduction to the rigidity of the metal structure in that framework, thus reduces the counter-force and vibrations during the operation. In the mean time, it also greatly cuts down the resonating noises generated from the operation due to gravity and vibrations.
