Abstract: Silver nanoparticles (AgNPs) are widely used in flexible electronic products for their superior physical and chemical properties. However, the thin films formed by sintering single-sized silver nanoparticles undergo many challenges due to their defects. The films formed by single small-sized AgNPs have high porosity, small grain size and many defects, while the ones formed by single large-sized AgNPs have larger grain size and less defects, but its sintering temperature and porosity are high. In this context, the mechanical properties of the films mixed with 10 nm and 50 nm AgNPs were investigated by finite element simulation to enhance the mechanical stabilities, service reliabilities and electrical conductivities of the sintered structure of AgNPs, in which the 10 nm AgNPs serve as the “filler” to increase the initial stacking density and weld the large AgNPs together, while the 50 nm AgNPs play as the framework to decrease the initial crystallographic defects and stabilize the sintered structures. In the simulation, the filling spacing between large nanoparticles is selected as a parameter to characterize the mixing ratio of large and small nanoparticles. Simulation results showed that when the spacing was short, the small particles were subjected to uneven stress in the filling area, and cracks were easy to occur. When the spacing was too long, the film strength decreased due to the increased number of pores. The results showed that the mechanical properties were superior when the spacing was 50 nm in mixed mode.