A tubeless air valve stem has a body, an airtight element, and a sleeve. The body has a passage, a through hole, and at least one side hole. The passage is formed on a top end of the body. The through hole is formed through a bottom end of the body and is in communication with the passage. The at least one side hole is formed through an outer surface of the body and is in communication with the passage. The airtight element is disposed around the body. The sleeve is disposed around the body for closing the at least one side hole. Gas or liquid can be injected into a tubeless tire via the at least one side hole. The intake efficiency of the tubeless air valve stem can be maintained and is not influenced by the remaining reinforcing agent.