High-gradient magnetic filter and method for the separation of weakly magnetisable particles from fluid media (2) in a circuit, embodied as a compact, low-maintenance unit with low repair requirements, comprising a housing (1), for the high gradient magnetic filter, with means for directing the flowing medium (2) in a pipe system with a feed (3) and return (4), a magnetic circuit (5), forming the high-gradient magnet filter in which at least one filter (8) is arranged in a filter chamber (7), formed between the pole faces (6) of the magnetic circuit (5), through which the medium (2) for purification flows, at least one permanent magnet (9), arranged in the magnetic circuit (5), for generation of a magnetic field between the pole faces (6). The magnetic circuit (5) is separated and sealed off from the flowing medium, the magnetic field between the pole faces (6) may be alternately switched on and off by means of the permanent magnet (9), whereupon the discharge and the operation of separating off the particles from the flowing medium may be achieved simply and economically.