The single-phase Zn-doped n-type Ba8Ga16-2xZnxGe30+x clathrates were prepared by melting reaction method combined with spark plasma sintering (SPS). Influences of substituting Zn for Ga on the thermoelectric transport properties of the compounds were investigated. Research results indicate that the electrical conductivity of n-type Ba8Ga16-2xZnxGe30+x compounds increases gradually with the increasing of Zn substitution fraction x. The Seebeck coefficient decreases gradually with the increasing of x. When Zn replaces Ga entirely, the electrical conductivity of Ba8Zn8Ge38 compound drops rapidly and its Seebeck coefficient increases suddenly. Zn substitution fraction x dependence of the thermal conductivity and lattice thermal conductivity are similar in the temperature range from 300 to 1000 K.When xx,lattice thermal conductivity decreases gradually. When x>4, with the increase of x,lattice thermal conductivity increases gradually.In all n_type Ba8Ga16-2xZnxGe30+x clathrates, Ba8Ga8Zn4Ge34 compound has the greatest ZT value, and its maximal ZT value reaches 085 at about 1000K.