A 3-dimension vision sensor for red Fuji apple harvesting robot was presented. Lasers with sensitive wavelength were selected as active lamp-house according to the reflectance characteristic of apple plant, to scan apple plant under the drive of stepping motors. And recognition of apples depended on laser reflectance difference of plant, positioning of apples was accomplished based on triangulation. ARM7 microchip LPC2114 was used as the CPU, PSD was used as the signal receiving sensor. In order to eliminate the noise of environment, optimal design of circuit and mechanism was considered. The result of experiment indicated that the output signal of system was stable ranging from 150mm to 750mm, with the maximum error of 13mm.