Organometal halide perovskites have demonstrated excellent features compared to conventional optoelectronic materials. To date, the perovskite films have generally been fabricated by either spin coating or vapor deposition. However, both methods cannot simultaneously meet large scale and low cost of production. Here, a simple, low-cost and high-throughput strategy was proposed to fabricate perovskite thin films, which were further applied in photodetectors. First, lead compound nanoparticles were synthesized by a solvent precipitation method, then a paste with the lead compound nanoparticles was screen printed to form PbO films involving calcination, and next the PbO films directly reacted with CH3NH3I solution to convert into CH3NH3PbI3 films. The CH3NH3PbI3 films consisted of micron crystals, whose sizes can be effectively controlled by adjusting CH3NH3I concentration. Furthermore, the CH3NH3PbI3 films were applied in photodetectors, which showed good performance with high sensitivity and fast response.