The effects of the substitution of Li for Mg in Mg1-xLixB2(x=0, 0.1, 0.2) on their structure and superconductivity have been investigated. It has been found by X-ray diffraction that the substitution of Li for Mg with x=0.1 and 0.2 does not cause phase transformation in these samples. However, the measurements of temperature-dependent normalized magnetization indicate the loss of superconductivity with the increase of the Li content in these samples.