RF reflectometry is a promising technique for spin qubit readout, suitable for large-scale integrated qubit systems by combination with multiplexing techniques and gate-based readout. However, in such a system, it is suspected that the accuracy of RF readout of individual qubits can be degraded by crosstalk among dense RF readout lines. In this study, we propose a mixed-mode RF reflectometry to reduce the effect of the crosstalk and verify its effectiveness by electromagnetic field simulations. The results of the simulations show the possibility of sup-pressing the effects of crosstalk by using mixed modes.