An automatic visible spectrometer based on a non-collinear acousto-optic tunable filter (AOTF) is constructed for high-speed spectrometry. Its spectral filtering characteristics, such as relationships between the radio-frequency (RF) driving frequency and the output central wavelength, the output bandwidth and the central wavelength, its typical spectral point spread function (PSF), and so on, are studied systematically. The preliminary measurement results of AOTF spectrometer show that it is a solid-state, high-speed, easily controllable by computer-programming, rugged and compact spectroscopic device in comparison with a conventional grating spectrometer, and has the potential for widespread spectrometric applications.