The analytical evaluation indexes for three signal distortion errors of BOC(Binary Offset Carrier) signals were developed. Then the proposed evaluation indexes were used to evaluate the distortion errors of BOC(14,2) and MBOC(6,1,1/11) signals, which were the advised basis signals of BeiDou global satellite navigation system. The proposed distortion error evaluation indexes can be used to evaluate the distortion errors of modern global navigation satellite system signals, and it has directive significance to modern signal design and integrity monitoring.