Post tension floors (PT) are one of the most widely used system which are very effective method regarding ultimate and serviceability limit states. A numerical model for discretized the two-way reinforced concrete flat slab with different system is investigated by using RAM software. The effects of different parameters are investigated in this study. Parameters investigated include concrete strength, thickness of the flat slab, different values of jacking (force (P) / area of strand (A)) and also, study the flat slab with opening by changing the values of P/A. Results indicated significant effect of PT system in the flat slab by decreasing the deflection. Also, the magnitude of the bending moment is reversed at one internal column by increasing the value of P/A for large thickness.