Abstract: In order to study the influence of multipath code tracking error on multipath carrier tracking error, the multipath carrier error of Costas carrier tracking loop was analyzed when the non-coherent early minus late power mode code tracking loop was used, and the multipath error model of Costas loop was established in the presence of single multipath. The established model indicates that the influence of multipath code tracking error on multipath carrier tracking error can be expressed as the influence of multipath parameters and correlation space on carrier tracking error. The theory analysis and simulation results show that the mean carrier tracking error is zero in the presence of single multipath, and the maximal carrier tracking error is less than π/2 when the correlation space is smaller than one chip. It also indicates that the multipath parameters have more influence on the carrier tracking error than the correlation space.