Unconventional aircraft configurations, such as biplane, joined-wing, tandem-wing, and box-wing configurations, have considerable application potential due to aerodynamic interference between the front wing and rear wing airfoils. Here, the aerodynamic interference of a two-dimensional front wing and rear wing airfoil system with different relative positions was simulated using a computational fluid dynamics (CFD) method, and the significance of the correlations between the aerodynamic coefficients and stagger or gap variations was investigated by ANOVA. The results indicate that the front wing and rear wing aerodynamic coefficients are distributed unilaterally with stagger and gap variations at a small angle of attack, although regional differentiation behavior was observed for an angle of attack exceeding 4°. The fake stall phenomenon, which is caused mainly by a decrease in the front wing upper surface suction force, is proposed and discussed. The significance level analysis results highlight that (1) the rear wing lift coefficient is the most sensitive to stagger and gap variations among the four lift and drag coefficients, and (2) the front wing lift coefficient is hardly affected by the stagger variation.