Magnetic field control technology is an important way to improve the interruption capability of vacuum circuit breaker.The axial magnetic field（AMF）can keep the arc diffuse

while

the transverse magnetic field（TMF）can drive the arc to rotate at high speed between electrodes with purpose of reducing contacts ablation. In recent years

a new type of composite magnetic field（TMF-AMF）contacts has attracted widespread attention

which can

in case of small current

keep the arc diffuse and

in case of sufficient high current and appearance of constricted arc

drive the arc to rotate. In this paper

the composite magnetic field contacts with two different structures are designed. First

the magnetic field of the two kinds of contacts is analyzed and the optimization in structure is performed. Then

the triggered arc experiments under fixed clearance are carried out and the arc characteristics of the two structures are compared.The study results show that the composite contact of the first structure can make full use of the whole contact plate

while the composite contact of the second structure can keep the arc near the inner contact plate

cannot make full use of the outer contact plate and be more prone to fusion of metal.