A cap assembly and a lithium secondary battery with the same, in which a shape of a safety vent of a cap plate is such that the safety vent is easily fracturable under low pressure even if the safety vent has a relatively large thickness, thereby improving reliability and safety of the lithium secondary battery. The cap assembly cap plate has a safety vent including at least one first directional weak component and at least one second directional weak component which is connected to the first directional weak component.