Abstract: To clarify the key factors affecting ROP improvement under different working scenarios, theoretical analysis, laboratory tests and field trials were conducted to reinterpret the corresponding relationship between ROP and WOB, and the influence mechanisms of rock lithology, drilling parameters, and cutters/bits on ROP improvement were also discussed. The study shows that both single-cutter cutting and full-scale bit rock-breaking follow the same variation law of mechanical specific energy (MSE) with depth of cut (DOC). Combined with the definition of mechanical specific energy, it is found that the ROP-WOB relationship exhibits four characteristic stages: inefficient rock-breaking, effective rock-breaking, high-efficiency rock-breaking, and abnormal interference. Notably, the effective rock-breaking stage has rarely been reported in previous publications. Then, it can be deduced that rock lithology determines the baseline of ROP, while rock lithology and drilling parameters jointly govern the ROP values. The advantages of cutters and bits in affecting the ROP improvement are mainly manifested in the effective rock-breaking stage, i.e., before the linear correlation between ROP and WOB is established. On this basis, to address limitations on energy transmission for rock breaking in ultra-long wellbores such as ten-thousand-meter deep wells and long horizontal sections, several promising solutions for high-efficiency rock-breaking under low WOB were explored from the perspectives of cutters and bits: (1) Under the same WOB, larger DOC and higher ROP can be achieved by optimizing cutter shape and reducing cutter density; (2) By breaking the conventional tip profile design and cutter arrangement strategies of bits, the WOB required for rock-breaking can be reduced.