A modified push-out method was used to explore the bond characteristics of the mortar–rock interface in an anchor system at different loading rates. Under a high loading rate (≥ 1·12 × 10⁻⁴ s⁻¹), stick–slip behaviour, which is usually used to describe the mechanism of earthquakes, was observed at the mortar–rock interface for the first time in this experimental research. The test results showed that the load–displacement curve under a high loading rate included four stages: elastic deformation, interface softening, residual friction and stick–slip oscillation. A micro-mechanical model of bond–slip at the mortar–rock interface was also developed. A series derivation revealed the relationships among the dilatancy stress of the mortar–rock interface, the loading rate and the stress drop of stick–slip. The mechanism of stick–slip behaviour at the mortar–rock interface was theoretically established. The modified visco-elastoplastic constitutive model established to describe the stick–slip characteristics of a mortar–rock interface was verified with experimental results using Abaqus software.