Based on the general theory of magnetic flowmeter, a study on the magnetic flowmeter at very low flow rate is reported in the paper. Firstly, the structure of the transducer is designed using the equivalent cross-section area method and the weight function and head loss are calculated. Secondly, having compared several digital signal processing (DSP) methods, the best one-base line method is adopted. On the basis of these, a prototype is developed by use of single chip microcomputer (SCM) technology, to realize the meter's intelligence and some other effective functions. Finally, the prototype is tested according to the relevant verification regulations, and the satisfactory results have been obtained.