Ingenious construction of the state-of-the-art models of electrophosphorescent hosts for uncovering the deep role of different molecular modifications in PhOLEDs performances is crucial for rational cumulative improvements of the device efficiency and further for accelerating their commercialization. A series of conjugation-interrupted spiro[fluorene-9,9’-xanthene](SFX)/9-arylfluorene (AFs) hybrid host materials have been designed and synthesized by concise two-step reactions, which have been demonstrated to serve as universal hosts for low voltage blue, green, red and single-emitting layer white PhOLEDs. By varying the eletronegativity and position of the bulky AF substitutes, two independent selective fine tuning of frontier molecular orbital energy levels without interference of high triplet energy level (T1) have been realized. This offers either the facilitated hole- or electron- injection/blocking without influence of their optical properties, which can well explain the corresponding RGB PhOLEDs performances. This investigation provides good guidance for future rational design of high-performance PhOLED hosts by accumulative structural modifications.