Abstract: In order to achieve the parallel, non-contacting and real-time measurement of filament diameter, a real-time and fast detection system of arrayed filament diameter was designed based on the complex programmable logic device (CPLD). Arraying the sensing system and solving diameters by CPLD, the multiple filaments were measured in parallel. The load of the data transmission of system was significantly reduced, the solving time of diameter was shortened, the detection frequency of diameter was increased to 5 kHz and the parallel measurement of 24 arrayed filaments was realized. The repeated accuracy of the dynamic measurement of system is 3.5 μm and 8.3 μm within the diameter range of 0.1 mm~0.3 mm and 0.3 mm~1.0 mm, respectively, and the absolute value of percentage of repeatability error in dynamic measurement is less than 1.21% and 1.43%, respectively, which meets the requirements of real-time and fast detection of arrayed filament diameter.