The effect of ion mixing on the growth of single-mode Richtmyer–Meshkov instability (RMI) at the carbon-hydrogen plasma interface is investigated using hybrid fluid-PIC simulations. It is observed that ion mixing primarily suppresses RMI growth by influencing the Atwood number and ionic kinematic viscosity, particularly for high wavenumber. By considering the effects of Atwood number and ionic kinematic viscosity, an analytical model for the growth of single-mode RMI at the plasma interface is developed, which demonstrates good agreement with data obtained from hybrid fluid-PIC simulations. This study offers new perspectives on the development of RMI and provides valuable references for future experimental and theoretical research.