High conductive graphene flexible circuits are printed through 3D printing. PLA are chosen as the substrate of graphene. Graphene can be homodispersed in the PLA substrate. Display omitted •3D print technique is used to print flexible circuits.•Highly conductive PLA-graphene composites are fabricated for 3D printing.•2D and 3D flexible circuits are printed rapidly.•The flexible circuits exhibit superior conductivity and mechanical properties. Fused depositing modeling (FDM) is a fast, efficient process among 3D printing techniques. In this paper, we report the fabrication of the 3D printed flexible circuits based on graphene. Modified two-step in-situ reduced method is used to synthesize reduced graphene oxide (r-GO), whose conductivity can reach to 600S/cm. Polylactic acid (PLA) and r-GO are mixed by melt blending. The SEM images show that the r-GO can be homogenous dispersed in the PLA. The 3D print-used composites filaments with the diameter of 1.75mm are fabricated through melt extrusion. The conductivity of the composite filaments from 3D printer can reach to 4.76S/cm (6wt% r-GO). The orientation of r-GO occurs during the extrusion process, which contributing to increase the conductivity of the filaments. The composite also exhibit superior mechanical property. The printed 2D and 3D flexible circuits have strong interface bonding force between the layers. The filaments from 3D printer can replace the copper wire because of the high conductivity. This arbitrary 3D graphene-based structure printing technic may open a new prospect in electronic and energy storage fields.