In this study, poly(lactic acid) (PLA) ultrafine fibers have been prepared by electrospinning method using mix-solvent. The results showed that the variation of solvent ratio (N,N-dimethylformamide (DMF)/Dichloromethane (DCM)) could change the surface morphology of PLA nanofibers. By adjusting the solvent ratio, the quercetin release rate from the fiber membranes could be controlled. Furthermore, by adjusting the PLA concentration, the nanofibers without beads could be obtained. After addition of quercetin to polymer solution, the spindle-shaped beads on the fiber disappeared, but surface morphology of the fiber changed little with increase in quercetin dosage, and the release rate of quercetin increased with increase of quercetin dosage.