The process of work done on the system by the external force is equivalent to the process of change in system state. The thermodynamic relations of coupled bistable system based on single stochastic trajectories are established by using microcosmic dynamics and macroscopic thermodynamic methods, according to the stochastic dynamics described by Langevin equation. The transmission and conversion relations of energy are quantitatively characterized via interaction of force and work of coupled system, which reveals the coupled system exhibiting stochastic energetic resonance phenomenon. Through analyzing relationship between work done and energy, the physical nature of produced stochastic resonance is further revealed.