In this work, highly crystallized and lengths up to a centimeter organic-inorganic hybrid perovskite CH3NH3PbI3 (MAPbI(3)) microwires (MWs) have been prepared via a solution-based blade coating and slow solvent evaporation method. And a two-step growth mechanism was proposed to explain the formation and growth of the MAPbI(3) MWs. Further, the as-prepared MWs were used to fabricate photodetectors and their photoresponse characteristics were tested and detailedly analyzed. The results reveal that the devices presented stable and repeatable photocurrent responses. A high on/off photocurrent ratio of 0.84 x 10(4), a photoresponsivity of 0.04 A/W, a specific detectivity of 0.6 x 10(12) Jones, and a fast response speed of 178/173 mu s were realized in the prepared MAPbI(3) photodetectors. More importantly, even without encapsulation, the proposed photodetectors demonstrate remarkable operation stability, above 80% of the photocurrent has been retained after a long running time (50,000 s, 45-55% humidity). After 60 days storage without encapsulation in air ambient, the proposed photodetectors can be efficiently sustained, demonstrating a strong ability to resist the water and oxygen degradation, greatly superior to reference photodetectors constructed with MAPbI(3) thin films. This work opens up an exciting opportunity for using MAPbI(3) MWs for high-performance and low-cost photodetectors applications.