Commercial carbon-based perovskite solar cells have rapidly developed due to its low cost and long-term stability. However, commercial carbon paste as counter electrode always produces a large number of defects at the perovskite interface, thereby greatly affecting the performance of the perovskite solar cells. In this work, a grinding process is used to compact the thin carbon film. The process effectively eliminates defects and improves the extraction efficiency of holes from the photoexcited layer, resulting in 21.2% increase in the efficiency of the carbon-based perovskite solar cells. In addition, open-circuit voltage decay on the order of tens of seconds is analyzed in detail. A new capacitor-like model is established to successfully explain the hysteresis phenomenon. Perovskite solar cells show 700 h of stability with ground carbon counter electrode.