A fan unit assembly includes a fan rack, fan units and handles. The fan rack includes a carrier and parallel partition boards erected on the carrier to define fan-disposing regions. The partition board has at least one first positioning part and at least one first guiding part facing the corresponding fan-disposing region. The fan unit has two side surfaces and a front surface. The front surface connects the side surfaces. The side surfaces respectively have a second guiding part engaged with the first guiding part. The fan unit is suitable to move along the first guiding part through the second guiding part. The handles are disposed at the front surface and both ends thereof are bent to form two pivot portions respectively pivoted on the side surfaces. Each pivot portion has a second positioning part. When the handle rotates towards the front surface, the positioning parts interfere with each other.