Abstract: The phenomena of rock mass slope with multi-weak interlayer can be found in real engineering frequently. It is worthy to study the influence of multi-weak interlayer on failure of rock mass slope. Based on the shear strength reduction finite element method, stability and failure surface of rock mass slope with different parameters had been studied, the failure mechanism of rock mass slope containing multi-weak interlayer has been analyzed. It can be found that the stability of consequent rock slope decreased first and increased later with increasing of rock stratum inclination which got its minimal value at 30° of rock stratum inclination. The stability of anti-dip rock slope fluctuated with increasing of rock stratum inclination which got its maximal value at 135° of rock stratum inclination. Whether consequent rock slope or anti-dip rock slope, the stability of slope decreased with angle of slope increased. Although, the stability of rock slope reduced or weakened by multi-weak interlayer, the failure and stability is controlled by parameters of rock mass mostly.