Single-crystal line, precise size-controlled nanowires and ultralong microwires with lengths reaching several millimeters of organic semiconductor I were prepared in large scale by cast assembly. The size and density of the nanowires and microwires could be controlled by simply adjusting the concentration of 1 in casting solutions. More importantly, the formation of these nanowires and microwires showed no substrate and solvent dependence and was orientation controllable. Highly reproducible and sensitive photo response characteristics were observed in these nanowires and microwires. Fast and reversible photo-switchers based on multiple or individual single-crystal microwires were fabricated via "multi times gold wire mask moving" technique with switch ratio over 100.