This report is the summary of what has been done for my TP4 project in second semester at "laboratory of quantum magnetism (LQM)" under the supervision Prof.H.Ronnow. This project is the continuation of first semester regarding to measurement of specific heat of BCPO. The subject is to measure and compare the specific heat of two samples, BiCu2PO6 and BiZn2PO6 under applying pressure. This comparison leads to understanding the change in magnetic structure of BCPO, which has Spin-Gap, after replacing its Cu ion with non-magnet element Zn. Zn has no magnetic momentum, so its specific heat behavior is a good approximation of phonon interaction part of BCPO, and by subtracting this part, we can find the magnetic behavior of BCPO.