Abstract: In order to study the effect of 3D printed negative Poisson's ratio polylactic acid (PLA) lattice on the flexural performance of high-strength concrete (HSC) beams, four-point bending tests were conducted on plain HSC beams, octet lattice reinforced HSC (O-HSC) beams, re-entrant honeycomb lattice reinforced HSC (H-HSC) beams and re-entrant triangular lattice reinforced HSC (T-HSC) beams. The results indicated that the PLA lattice reinforced HSC beams exhibited progressive fractures from bottom to top under the bending load. The load-deflection curves of O-HSC beams showed an approximately linear increase and a stepwise decrease, while the curves of H-HSC beams and T-HSC beams showed a stepwise increase and a slow and steady decrease. Compared with the octet lattice, the first cracking deflection and first cracking strength of the negative Poisson's ratio lattice confined HSC beams were reduced, but the peak deflection, flexural strength and flexural toughness were increased. The first cracking deflection, peak deflection, first cracking strength and flexural strength of T-HSC beams were 61.94%, 23.41%, 296.35% and 20.18%, respectively, higher than those of O-HSC beams. The enhanced ductility and strength of HSC beams can be attributed to: (i) there are more layers of re-entrant triangular lattice at similar volume fraction, (ii) the angle between the bar and longitudinal direction of the beam is small, and (iii) the node has larger cross-section.