A kind of combined hollow building plank with reinforcing steel bar in it, comprises the prefabricate lamella, the mould hull, the hidden rib, the upper plank, the mould hull fixed on the prefabricate lamella, setting the hidden rib between prefabricate lamella and the mould hull, and close together to them, overlaying the upper plank on the mould hull, and connect with the hidden rib for the integral whole, its characteristic lie in setting strengthening pole on the prefabricate lamella.Thus, the strength of the prefabricate lamella is high, the firm degree is big, it's not easy to come forth of craze, in the same time, the strengthening pole subject and spread the force of building plank in the mould hull, improved the mechanics function of the building plank consumedly, in addition, the building plank still has the character of structure is simple, the strength is high, the anti- transform, anti- vibrate the function is good, construction convenience etc.