A rotatable vehicle seat frame assembly has a main frame, at least one first seat frame, at least one second seat frame, and at least one elevatable desk. Each seat frame has a bottom sliding mechanism, a top sliding mechanism, and an angle-adjusting mechanism. The second seat frame further has a leg rest assembly. The bottom sliding mechanisms, the top sliding mechanisms, the angle-adjusting mechanisms, and the leg rest assembly enable the seat frame to be rotated into a flattened status in a limited inner space of a vehicle, enable the seat frame to be transformed between a passenger-mode and a cargo-mode, and enable the seat frame to be used as a bed during a long trip. When in the passenger-mode, the position of the seat bracket and the angle of the back support bracket may be adjusted to facilitate convenience, and to provide more use modes in a limited inner space with the elevatable desk.