Abstract The rock strength in drilling formation means the rock crack strength. It is related not only to drilling parameters,but also to character of rock formation. Formation pore pressure is an important factor to affect rock strength. Based on experiment and site data,the relationship between rock strength and formation pressure is found and applied to detection of formation pore pressure. The applications of the method in some wells at Tarim Basin of Xinjiang of China show that the presented method is better than traditional one.