The invention discloses a method for eliminatinginfluences of an annulus internal liquid in RPM-C/O well logging. The method comprises the following steps: (1) drawing well logging curves of C/O and C/H of the annulus internal liquid of a borehole, adjusting scale endpoint values displayed by the C/O curve and the C/H curve, and finding out an envelope region when the C/H curve coincides with the C/O curve in a well section employing water as the annulus liquid; (2) calculating oil holdup YO in a well annulus according to the envelop region in case of well section coincidence; and (3) achieving correction on the C/O curve according to the relationship between the oil holdup YO in the well annulus and the stratum carbon-oxygen ratio C/O. According to the method, by the sensitivity difference and correlation of the C/H curve and the C/O curve on the oil holdup of the annulus liquid, the C/O curve of the well section influenced by the annulus liquid can be effectively corrected.