Using polylactic acid (PLA) as raw material, a spinning solution is prepared using dioxane (DIOX)/acetone (AC)/N, N-dimethylformamide (DMF) as solvent. PLA nanofiber membranes are prepared by needle and needleless electrospinning respectively. The effects of solvent ratio, PLA mass fraction and spinning voltage on spinnability and fiber morphology are studied, and the forming mechanism of needle and needleless electrospinning fibers is analyzed. The results show that there are differences in the effect of solvent ratio on the spinnability of PLA needle electrospinning and needleless electrospinning, but the fiber formability law is consistent. Similar fiber diameters are obtained after needle and needleless electrospinning, which can be explained by the simplified jet stretching model.