This paper presents the test results of an experimental study aimed at investigating the flexural behavior of prestressed high and normal strength concrete filled fibre-reinforced polymer (FRP)- rectangular tubes (CFFT) beams. Two unbonded post-tensioned (PCFFT) beams were constructed with different concrete compressive strength ranged from 40 to 70 MPa. All beams had identical cross-sectional of 305 x 406 mm(2). The beams were tested under a four-point bending. The test results confirm the feasibility of using post-tensioned rectangular CFFT system for flexural members. The results indicate that the PCFFTs beams are capable of developing very high inelastic flexural deformations and ultimate capacity. High-strength and normal-strength concrete prestressed CFFT beams show almost similar inelastic load-deflection behaviors. While increasing the concrete compressive strength from 40 to 70 MPa enhanced the initial stiffness and load before cracking. After cracking, however, prestressed CFFT beam constructed with high-strength concrete exhibit only a 7% increase in the ultimate flexural moment capacity with no significant change in the ultimate deflection compare to normal-strength concrete beam. The proposed analytical model based on partially confined concrete model successfully predicts the flexural moment capacity of the tested beams with satisfactory accuracy on average of 1.08 +/- 0.03. However, further experimental tests are needed to better understand the flexural behavior of PCFFTs with a wide range of concrete compressive strength.