An end cover assembly of battery includes a battery end cover, a terminal substrate, an airtight insulating pad and a secure assembly. The battery end cover has first and second surfaces and a first opening. The terminal substrate is disposed on the first surface of the battery end cover and has a protrusion portion and a airtight ring, wherein the protrusion portion penetrate through the battery end cover through the first opening, and the airtight ring is disposed towards the battery end cover around the protrusion portion. The airtight insulating pad is sandwiched between the terminal substrate and the battery end cover. The secure assembly is disposed on the second surface of the battery end cover to collaborate with the terminal substrate for fixing the battery end cover and making the battery end cover and the airtight ring to press the airtight insulating pad to achieve an airtight effect.