The measurement of rock compacting is theoretically based on Terzaghi Equation

which takes incorrectly the difference of P

o

and P

i

as net confining pressure.A new equation P

o

= P

eff

+ ΦP

i

is proposed in this paper to calculate the net confing pressure correctly

and an improving measurement procedure is presented.The compacting factors obtained in lab must be converted into the value which is applicable to reservoir engineering when practical calculatoins are being operated.The conversion formula is established in this paper.