Abstract: Mixed stratum has significant influence on the efficiency of rock breaking and driving parameters of cut? ters. Aiming at the shield running tunnel section of lot 1 of Jinan urban rail transit R1 line in mixed stratum, penetration tests of the cutter in condition of rock samples with different strengths are conducted, and the effects of different penetration rates on rock breaking of cutter are studied. The test results show that: the larger the rock strength, the larger the invading-resistance coefficient and the impact load acting on disc cutter and more obvious of brittle failure; the effect of penetration rate on rock breaking of cutter is similar to that of rock strength, but the penetration load, load drop, critical penetration at jumping point are all in a logarithmical function relationship with penetration rate; the rock breaking process can be divided into four stages, namely compaction stage, dense core formation and development stage, crack cut-through stage and residual strength stage.