Poly(l-lactide-co-epsilon-caprolactone-diOH) (PCLA) with (ABA)(n) type is synthesized using poly(lactic acid) (PLA) and poly(epsilon-caprolactone) di-OH (PCL-diOH) via chain extending method. FT-IR, H-1-NMR, and GPC data demonstrate that PLA and PCL-diOH have reacted completely. The product is electrospun into ultrafine fibers subsequently. The optimum electrospinning parameters obtain from an orthogonal experiment are a solvent ratio (DMF/DCM) of 5/5, a polymer concentration of 28 wt %, a collector distance of 20 cm and a voltage of 18 kV. As a result, the average diameter of fibers is 0.77 mu m and the uniformity is above 80%. Via range analysis, it is found that the order of the influence on diameter is solvent ratio, applied voltage, collector distance, and polymer concentration, successively. Single effect of the four governing factors on diameter and morphology is also experimentally investigated. This may provide clues for obtaining fibers with various structures by controlling the parameters. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3600-3610, 2013