A serial fan frame assembly structure includes a first fan frame and a second fan frame. The first fan frame has a first and a second retainer, as well as a first and a second receiving slot; and the second fan frame has a first and a second receiving recess, as well as a first and a second post. The first and second retainer are configured for correspondingly engaging with the first and second recesses, while the first and second posts are configured for correspondingly engaging with the first and second receiving slots, so that the first and the second fan frame can be quickly assembled together in a manner capable of reducing vibration during the operation of a serial fan.