In this study, avermectin (AVM) was successfully dispersed in a cellulose acetate (CA) solution. CA/AVM composite fibers were fabricated by electrospinning the blending solution containing different amounts of AVM. Further investigation indicated that the composite fibers showed continuously changed morphologies with the concentration of AVM increasing. The electrospun fibers were characterized by field emission scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and thermal gravimetric analysis. The release behavior of the composite fibers was studied at pH = 7.4 and buffer media at 27 degrees C and the amounts of AVM at different release steps were determined by high performance liquid chromatography analysis. Furthermore, AVM release from the CA/AVM samples showed two stages-initial fast and later slow release. The two stages supplied a continuous release to achieve the effective utilization of AVM. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers