The invention discloses a moving iron type low frequency acoustic generator, comprising a basin rack, a supporter, a gasket, a quality sheet, a magnetic cup, a sound film, a front cover, a magnetic steel, a plywood, a printed circuit board, a voice coil and a rear cover, wherein the magnetic cup, the magnetic steel and the plywood form a constant magnetic circuit system, the constant magnetic circuit system and the supporter forms a vibratory magnetic circuit system; the supporter and the basin rack are subjected to integrated injection moulding in a structural manner of embedded part, the gasket is arranged between the quality sheet and the supporter, the edge of the sound film is fixed on the basin rack and the center of the sound film is connected with the vibratory magnetic circuit system, the front cover is arranged outside the sound film, a magnetic gap is formed between the magnetic cup and the plywood, the printed circuit board is fixed on the basic rack, one end of the voice coil is fixed on the rear cover, and the other end of the voice coil is inserted into the magnetic gap of the constant magnetic circuit system. The moving iron type low frequency acoustic generator of the invention with small volume can mainly be applied to some products which requires relatively low frequency but not large volume, such as portable fetal sound receiver, thus the fetal sound detected by the portable fetal sound receiver can be played.