The pantograph-catenary system is a crucial component in the electrification of rail transit, and its current collection quality directly impacts the operation of electrical equipment on high-speed trains. The method of applying a transverse magnetic field is proposed to improve the current receiving quality of the pantograph-catenary system. The variation laws of contact resistance, current stability coefficient, and current carrying efficiency of the pantograph-catenary system under an additional magnetic field were studied using a self-developed sliding electric contact experimental machine. The experimental results show that the additional transverse magnetic field can effectively reduce the contact resistance and improve the current-carrying efficiency. On this basis, the experimental data was quantitatively analyzed using path analysis method. By comparing the standardized path coefficients of the external transverse magnetic field with the contact current, contact pressure, and operating speed on the current carrying efficiency, the order of the influence of the four operating conditions on the current carrying efficiency was determined as follows: contact current > transverse magnetic field > contact pressure > operating speed. It has been confirmed that the additional transverse magnetic field has a significant effect on improving the current carrying efficiency of the pantograph, which has certain guiding significance for the design of new pantograph.