An experimental study of rock-breaking with an offset single cone bit was completed on the bit bench test equipment.Data such as transmission ratio,weight on bit (WOB),rate of penetration (ROP)and torque on bit were acquired in the experiments.Based on analyzing the experimental results,several conclusions were drawn as follows.The transmission ratio of the offset single-cone bit changed slightly with rotary speed of bit,weight on bit and offset distance.The rate of penetration of the offset singlecone bit increased with increase of WOB and offset distance.The torque on bit increased with increase of offset distance under the same WOB and bit rotary speed,decreased with increase of bit rotary speed under the same WOB.The rock-breaking mechanism of the offset single-cone bit was a scraping action.This indicates that the offset single-cone bit is a chipping type bit.