<p>The most prevalent epidemics are often caused by multiple pathogenic strains, which can present a significant challenge to disease control and lead to very complex dynamics. However, the spreading dynamics of two interacting diseases are not yet well-researched or explored. For this purpose, we formulate and analyze a two-strain <i>SIS</i> epidemic model with mass media in multiplex networks. Here, we consider the interaction process between two diseases with mass media in a multiplex network, where both diseases spread together within the same population. Through theoretical analysis, we derive an individual-based discrete-time model with different types of equilibrium points and perform stability analysis of equilibrium points. By bifurcating the equilibrium, we assess the epidemic threshold of single disease. The results show that the theoretical model is effective in capturing the time-evolution and steady-state behavior of the epidemic process. Furthermore, the simulation results indicate that mass media play a key role in the disease process. And it is also found that the epidemic threshold of one disease is not determined by all system parameters. Regarding the interactions between two strains, mutual promotion can increase the stationary infection density of the disease, but mutual inhibition leads to the opposite case. The current results are constructive to understanding the epidemic dynamics of two strains and the effect of mass media.</p>