Stereolithography (SLA) 3D printing utilizes photocurable resins to achieve additive manufacturing with high resolution. One of the major interests in this area is to develop more materials with different mechanical properties that can satisfy different application purposes. Previous research has employed thoil-ene chemistry to SLA printing of silicone. However, the toughness of this material is far less than its counterparts for molding. Herein, We added PDMS-grafted silica nanoparticles into siloxane resin and found that the toughness of cured nanocomposites can be enhanced to more than five times. More importantly, we managed to print these highly viscoelastic materials through a bottom-up SLA setup. Since a potential limit for SLA printing is the viscosity of such materials, we systematically studied the rheological behaviors of our suspensions and established a parametric model to illustrate recoating process during printing. We found that the pressure-driven flow is critical for printing such materials.