Pump pressure is one of the important parameters of diamond wire-line core drilling, which can reflect whether the operation is normal in the well. In order to further study the relationship between pump pressure fluctuation and the actual drilling operation for fast and safe drilling, on the basis of the actual pump pressure data of CUSD2 in Heyuanbei of Jiangxi and the related drilling data, a pressure loss calculation model for drilling circulation system is established. Comparing the fluctuation trend of theoretical pump pressure calculated by analysis model and actual pump pressure and using the model to the actual drilling, the pump pressure fluctuation in subsequent formation was predicted, it was found that 7MPa pump pressure safety value was no longer suitable for subsequent drilling, then the safety value was adjusted to 10MPa. The reliability was verified by the pump pressure fluctuation data of adjacent well. By the appropriate adjustment and correction, this theoretical model can be applied in wire-line core drilling in Heyuanbei and the whole Xiangshan area.