The effects of blended additive on properties of bio oil were investigated by adding n-butanol, dimethyl sulfoxide (DMSO) and ethyl acetate to bio-oil. The blended additive, which consisted of 2.421 wt% n-butanol, 2.327 wt% DMSO and 3.252 wt% ethyl acetate, was obtained through simplex lattice of mixture design. A 24 h aging experiment at 80 degrees C revealed that blended additive can improve bio-oil stability, and the effect of the blended additive was superior to that of a single additive. The viscosity of the bio-oil containing optimal blended additive was 8.21 mm(2)/s, whereas that of a single additive ranged within 8.89-9.78 mm(2)/s. During the long aging process (12, 24, 36 and 48 h), the increase in viscosity and water content of the blank group was larger than that of the control group. Thermo-gravimetric analysis (TGA) results showed that the residual mass fraction of the bio-oil rose with aging time, and the trend increase of blank was larger than that of control. Gas chromatography-mass spectrometer (GC-MS) findings showed that the content of phenols was highest in bio-oil samples and decreased with increasing aging duration. The total contents of ketones, aldehyde and furans diminished with aging time.