Recently, low temperature co-fired ceramic (LTCC) technology is widely used in sensors, actuators and microsystems fields because of its very good electrical and mechanical properties, high reliability and stability as well as possibility of making 3D micro structures. In this study, we investigated the effects of sputtering gas ratio and annealing temperature on the crystal structure of Pb(ZrTi)O3 (PZT) thin films deposited on LTCC substrate. The LTCC substrate with thickness of 400 ㎛ were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. The PZT thin films were deposited on Pt / Ti / LTCC substrates by RF magnetron sputtering method. The results showed that the crystallization of the films were enhanced as increasing O2 mixing ratio. At about 25% O2 mixing ratio, was well crystallized in the perovskite structure. PZT thin films was annealed at various temperatures. When the annealing temperature is lower, the PZT thin films become a phyrochlore phase. However, when the annealing temperature is higher than 600℃, the PZT thin films become a perovskite phase. At the annealing temperature of 700℃, perovskite PZT thin films with good quality structure was obtained.