The present invention proposes a prefabricated building frame structure unit, including prefabricated middle three-dimensional beam-column unit and / or side three-dimensional beam-column unit and / or corner three-dimensional beam-column unit, prefabricated floor unit, slab-beam-column connecting device, corresponding beam unit The longitudinal reinforcements of the slab-column connection device are connected to each other and the concrete is poured. The inside of the slab-column connection part in the slab-beam-column connection device coincides with the cross-section of the column unit, and the outside coincides with the slab-column installation hole of the prefabricated floor unit. The lower part of the slab-beam-column connection device The backing plate is placed on the top of the beam unit, and the prefabricated floor unit is installed from the top of the column unit through the plate-column installation hole matching the section of the column unit.