The full-potential linearized augmented plane wave method was applied to study the electronic and the magnetic properties of the compound pipz-H2[MnF4(HF2)](pipz=piperazine). The band structure, the total density of states, the partial density of states and the electron density were calculated to explain the electronic and the magnetic properties of pipz-H2[MnF4(HF2)] in the ferromagnetic state. It is found that the magnetic moment of the molecule mainly comes from the Mn atoms with partial contribution from the F atoms. The symmetrical σ /σ bonds via H atoms along Mn-F-H-F-Mn chains and the weak direct-exchange interaction between F(2), F(3)and Mn atoms have effect on the electronic structure and the magnetism of pipz-H2[MnF4(HF2)].