The present disclosure provides a charging control method, a charging trigger apparatus, and an online charging system. The method includes: generating, by a CTF, a resource quota request according to a trigger condition; and sending the resource quota request to an online charging system (OCS), so that the OCS determines a quota type and number after receiving the resource quota request, and allocates a quota for the resource quota request according to the quota type and number determined by the OCS, where the quota type and number are determined by the OCS according to the resource quota request. In the foregoing method, a problem that in the prior art, a charging control error occurs due to different determining bodies of a quota type is solved.