We propose a volume fraction based approach to effectively simulate the miscible and immiscible flows simultaneously. In this method, a volume fraction is introduced for each fluid component and the mutual interactions between different fluids are simulated by tracking the evolution of the volume fractions. Different techniques are employed to handle the miscible and immiscible interactions and special treatments are introduced to handle flows involving multiple fluids and different kinds of interactions at the same time. With this method, second-order accuracy is preserved in both space and time. The experiment results show that the proposed method can well handle both immiscible and miscible interactions between fluids and much richer mixing detail can be generated. Also, the method shows good controllability. Different mixing effects can be obtained by adjusting the dynamic viscosities and diffusion coefficients.