Abstract: The design of Janus-Helmholtz transducer driven by the iron-gallium (Fe-Ga) single crystal material is proposed. Because both the large low-field strain and high mechanical strength characteristics of Fe-Ga single crystal material and the structural advantages of Janus-Helmholtz transducer could be used effectively, it has the potential to meet the fast growing requirement of deep-water, low-frequency and broadband transducer. A series of theoretical analysis models for a Fe-Ga single crystal transducer with permanent magnetic bias magnetic field and annular closed magnetic circuit are established at first, including the linearization processing method of the magnetostrictive material parameters, the segmented magnetic circuit technique to refine the equivalent driving parameters according to the distribution of static and dynamic magnetic field, and the full impedance model to calculation of static impedance of transducer through the inductance loss. Then the optimization on the structural parameters and the electro-acoustic performance is done by the two-dimensional equivalent finite element analysis model. At last a prototype is made and measured. It is confirmed that the experimental results of the impedance and the transmitting current response are in good agreement with the predictions of the full impedance model and the equivalent finite element model respectively. The fundamental resonance frequency is 1000Hz with the transmitting current response of 176.4dB. The fluctuation of the transmitting current response is no more than 6dB in the frequency range from 875Hz to 2300Hz. And the maximum source level could reach 196.2dB when the driving current is 16.2A.