In a magnetic flux modulated DC superconducting quantum interference device (SQUID) readout, the matching transformer could realize the function of signal amplification and impedance matching, which is the key element of a low noise SQUID readout. We use a simulated DC SQUID readout to test the characteristics of matching transformer, study the transmission characteristics of transformer with different turns, and confirm its best turn ratio. In the coupling network that the transformer picks up voltage signals of SQUID, We also study the transmission characteristics of transformers with different matching capacitances, realize the matching of the parameters and the optimization in the transformer coupling network. At room temperature, for the matching transformer with a turn ratio of 1:20, when matching capacitance is 1 μF, the gain of output voltage source could reach 21.2 and its bandwidth could reach 210 kHz. Finally, in magnetic flux modulation DC SQUID readout, we evaluate the performance of the matching transformer.