Liquid crystal polymer nanofibers with a diameter ranging from 0.13 to 4.71 mu m were prepared by electrospinning from a main-chain liquid crystalline polyester, BB-5(3-Me). WAXD measurements showed that the formation and orientation of the ordered structure in the electrospun fibers were controlled by the fiber diameter formed during electrospinning. For BB-5(3-Me), the SmA structure with two layer spacings was formed in the fiber during the electrospinning. Under optimal spinning conditions, the SmA structure is highly oriented in the fiber. In addition, annealing transformed the metastable SmA structure in the BB-5(3-Me) fiber into stable SmCA one.