Polyvinylidene fluoride (PVDF) can be made electroactive by properly mechanical stretching and electric poling treatments of its film, which may be easily realized by single-step electrospinning. This technique is acknowledged as an effective approach to induce rich ferroelectric beta-phase in electrospun PVDF fibers; however, the investigation of dipole arrangement during the electrospinning process is still lacking. Here, the piezoelectricity of beta-PVDF fibers by electrospinning and forcespinning, a mechanical spinning process without static electric field bias, has been demonstrated. Results show that the electrospun fibers can generate piezoelectric voltage after deformation, while the forcespun fibers nearly show no piezoelectricity for the same condition, revealing that electric field during the electrospinning process can perform in situ poling effect and therefore induces preferred dipole orientation in electrospun PVDF fibers. Further experiments performed in this work show that piezoelectricity of the electrospun fibers increases with increasing fraction of beta-phase and/or the applied electric field strength of electrospinning, which provides good guideline for preparing high-performance piezoelectric fibers.