In an interfacial mass transfer process, the concentration gradient of the transferred component builds up in the vicinity of the interface. The concentration gradient may generate density difference near the interface. If the density gradient directs opposite to the gravity, the interface is known as in Rayleigh instability and Rayleigh convection may occur in case of perturbation. Rayleigh convection is an interfacial phenomenon usually observed in mass transfer processes and in material processing industries. In this study, a two-dimensional lattice Boltzmann method (LBM)is implemented for simulating Rayleigh convection, which is induced by interfacial mass transfer in the CO₂ absorption into liquid ethanol. The computations of concentration and velocity fields are based on a two-distribution model, which consists of the concentration and the density distribution functions of fluid particles in the lattice Boltzmann method. And the gravity difference due to the concentration difference is introduced into the model as external force. The established method is used for the simulation of two-dimensional liquid-phase Rayleigh convection induced by multiple discrete diffusion sources of CO₂ on the gas-liquid interface. The simulation results show that the concentration contours are consistent with the experimental results in literature. The effects of Rayleigh convection on the transport mechanisms are investigated by analyzing the Rayleigh convection and concentration contour patterns. By simulating the concentration field with the LBM, the instantaneous interfacial mass transfer flux of CO₂ can be obtained. It is demonstrated that when the Rayleigh convection occurs, the instantaneous interfacial mass transfer flux increases in the beginning and then decreases with time. Such behavior may be affected by the Rayleigh convection patterns and their evolutions.