Abstract Lead germanate, Pb5Ge3O11 (PGO), is known to be ferroelectric with a large pyroelectric property and relatively small dielectric constant. In this paper, we investigated the optimal conditions for the c-axis oriented PGO thin films. The effectiveness of oxygen (O2) as an oxidizing agent during in-situ growth of PGO thin films on YBCO/LaAlO3(100) substrates is studied as a function of substrate temperature. Films with c-axis preferred orient can be obtained at a substrate temperature of 650°C for 20min with oxygen pressure 26.6 Pa followed by subsequent annealing temperature at 400 °C for 30min to keep good YBCO layers.