The invention relates to the technical field of oil exploration, and particularly relates to a slip-sweep harmonic suppression method and device. The method comprises the following steps: acquiring slip-sweep relevant post data, and picking up the first arrival time of the relevant post data; performing complementary ensemble empirical mode decomposition (CEEMD) on the relevant post data to obtain a group of intrinsic mode function (IMF) components; analyzing the distribution condition of harmonic in the IMF components, and determining the IMF components containing the harmonic and the IMF components not containing the harmonic; performing harmonic attenuation on the IMF components containing the harmonic from the first arrival time; and reconstructing the IMF components after harmonic attenuation and the IMF components not containing the harmonic to obtain harmonic-removed relevant post data. The method and the device effectively suppress the slip-sweep harmonic without focal force signals, and improve the signal-to-noise ratio of seismic data.