The compression properties of cementitious backfill composite (CBC) is strong, but their tension properties are weak and presents little ductility because of their low fatigue crack growth rate and resistance. Thus, proper reinforcement techniques are needed to improve CBC's ductility without rupture. This paper deals a system for boosting CBC's ductility by reinforcing it with several types (e.g., ordinary resin OR, transparent resin TR, and nylon NY) and shapes (e.g., hexagon, cube, and rhombus) of 3D printed polymeric lattice (3D PPL) by agreeing the digital image correlation method. Specimens were subjected to three-point bending and SEM experiments to study their flexural and microstructural behavior. Results shown that: the flexural strengths of OR and NY 3D PPL reinforced CBC specimens were larger than TR and non-3D-PPL (N-3D-PPL) reinforced ones. But TR 3D PPL reinforcement effect was not so vibrant. For an ideal flexural strength, the best type and shape of 3D PPL were OR and rhombus, respectively. The deflection of 3D-PPL reinforced CBC specimens was larger than those N-3D PPL reinforced ones. For an ideal deflection value, the optimal shape and 3D PPL types were cube and OR. 3D PPL reinforced CBC specimens exhibited great ductility and toughness while N-3D PPL reinforced ones exhibited obvious brittleness. The most abundant elements were oxygen, calcium, and silicon, which gathered in the large amounts around C-S-H gels' location. Finally, the outcomes of this work state that 3D PPL has great potential for converting brittle CBC into a ductile material without dropping its hardening performance.