An experimental investigation is performed on a single jet issuing into a flow in a pipe. The pressure of the flow in pipe is measured under the condition when there is a right angle between the jet and the mainstream and the velocity of the jet is 1 to 6 times of the mainstream. The results show that, there exists a jet core with skewing downstream near the entrance port; the pressure in that core increases slightly with the fluid incidence. Outside the core, the pressure of the flow inside the pipe increases significantly; the pressure increment is correlated with the velocity of the jet quadratic dependence.