Modern trams have the characteristics of short construction period, low total investment and quick performance. However, with the construction of tram project, the investment of power supply system is still very high, and the design scheme is not the same. In this paper, according to the characteristics of modern trams, the design scheme of power supply system of modern tram is analyzed. Based on the comparative analysis of urban rail transit, this paper draws on the mature experience of similar power supply design in other industries. This paper recommends that the external power supply using 10kV decentralized power supply, medium voltage ring network with a single ring network form, and suggests that the ring switch using load switch ring network cabinet instead of circuit breaker cabinet, to meet the electrical and mechanical equipment requirements and save the effect of investment.