Polybenzoxazole (PBO) electrospun nanofiber belts were successfully prepared in three steps, low-temperature polycondensation to synthesize precursor of PBO with 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 3,3'-dihydroxybenzidine (DHB), hydroxy-containing polyamic acid (OH-PM), electrospinning OH-PAA solution to obtain nanofiber belts and thermal conversion to get PBO nanofiber belts. The structures of polymers were characterized by FT-IR and H-1 NMR. The thermogravimetric analysis showed that 5% weight loss temperature was very high up to 643 degrees C in N-2 atmosphere. CMT-8102 Electromechanical Universal Testing results indicated that PBO nanofiber belts possessed excellent mechanical properties with tensile strength of 525 MPa and Young's modulus of 8.2 GPa. Further more, an excellent thermal mechanical properties tested by thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) showed that both the retention of tensile strength and storage modulus of PBO nanofiber belts were above 80% when the samples were heated at 350 degrees C in N-2 atmosphere. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.