We study the surface defect gap solitons in an intefface between a defect of one-dimensional dual-frequency latticesand the uniform media.Some unique properties are revealed that such lattices can broaden the region of semi-finitegap,and the semi-finite gap exists not only in the positive and zero defects but also in the negative defect;unlike in theregular lattices,the semi-finite gap exists in the positive and zero defects but does not exist in the negative defect.Inparticular,stable solitons exist almost in the whole semi-finite gap for the positive and zero defects.These propertiesare difierent from other lattices with defects.In addition.it iS found that the existence of surface dual-frequency latticesolitons dOes not need a threshold Power.