The invention relates to a detector used for detecting number of viscose filament and diameter of single filament, comprising an electrostatic divilicating device, a light source, a miniature camera, a step motor angle regulation device and a computer display treatment system. The light source (20) and the miniature camera (21) are positioned at the top end of and form a probe together with the step motor angle regulation device, the probe is placed at the lower part of the detecting window (10) of a working table (7), and the electrostatic divilicating device (5) is placed at one side of thedetecting window (10) on the working table (7); the computer display treatment system comprises a dynamic picture liquid crystal display, a computer host (11) and a chip master control circuit (47) to realize relevant functions switching and relevant interfaces thereof. The detector can visually inspect the number of the viscose filament and count the number of the single filament and automatically detect the diameter of the single filament.