Porous fibers are being extensively studied in many different fields due to a large specific surface area coupled with high porosity. In the study, morphology, structure and tensile properties of polylactic acid (PLA) porous nanofibers were studied. Crystalline and amorphous PLA porous nanofibers were electrospun through two kinds of spinneret systems from mixed solvent of DCM and DMF in highly humid environment. The results showed that the variation of take-up velocity affected the porous morphology of resultant nanofibers. And this take-up velocity effect was more obvious in the cases of channel-based spinneret and amorphous PLA. In the case of crystalline PLA, the study of structure-property relationship showed that an increase in take-up velocity led to more packed internal structure, which could contribute to the enhancement in tensile properties. In addition, tensile properties of amorphous PLA porous nanofibers could be manipulated by surface morphology control via channel-based electrospinning system.