Electrospun poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) fibers were collected by using I counter electrode collector or I rotating disk collector. The molecular orientation and mechanical property of single PHBV fiber were studied. 2-D wide-angle X-ray diffraction and polarized Fourier transform infrared spectra of the macroscopically aligned fibers confirmed the orientation of polymer chains, with PHBV chains preferentially oriented along the fiber axis. The degree of orientation increased with increasing fiber take-LIP velocity. X-ray diffraction pattern also indicates the development of beta-form crystal in electrospun PHBV fibers collected at all angular velocity of 1500 rpm. The thermal behavior of electrospun PHBV fibers was Studied using modulated differential scanning calorimetry. The tensile properties of single electrospun PHBV fibers were Studied using a nanotensile tester. Our results indicate that electrospun PHBV fiber with a higher degree of molecular orientation exhibits a higher tensile modulus and strength but lower strain at break.