To quantitatively investigate the aerodynamic features of tandem configurations with respect to the relative geometric positions, on account of the preliminarily conducted wind tunnel experiments, unsteady computational simulations on a group of tandem configurations from NACA0030 have been carried out using our in-house codes based on hybrid computational grid, and the effects of spacing on general aerodynamic features and vortex structure in flow field at angles of attack varying in the range of 0° to 20° have been compared and presented in low Reynolds number flow of Re = 1.2 × 105. Final analysis of the computational results indicates that the closer the normal distance between the two airfoils, the more severe the aerodynamic interference effect. When the relative normal distance is less than 1.0, the aerodynamic interference effect of the walls of the two airfoils is more significant. When the relative normal distance is greater than 2.0, the aerodynamic interference effect of the two airfoils can be neglected because the variation of aerodynamic efficiency of the tandem airfoils is very small comparing to the isolated airfoil. It is worth noting that for certain tandem configuration with specific normal relative positions, aerodynamic interaction effects can generate thrust rather than drag. In addition, compared to single configuration, the overall aerodynamic efficiency of a tandem configuration is significantly higher at angles of attack higher than 14°, with an increase of up to 25%. Therefore, tandem configuration can be used as an alternative aerodynamic design plan for low Reynolds number aircraft layout.