This study employs numerical simulations to investigate the impact of pitch relative positions (PP) and axial relative positions (AO) on tandem stator performance and corner stall. The results indicate that two distinct types of corner stall behavior are exhibited. With PP values of 0.50 and 0.60, the rear blade stalls first, while with values of 0.70 to 0.90, it is the front blade that stalls first. Additionally, there is a trend for corner stall to be delayed as PP value increases, which is attributed to PP changing the load distribution between front and rear blades. Corner stall is also delayed as AO increases. The mechanism is that the adverse pressure gradient of the suction surface boundary layer in the root regions decreases with AO increasing, which delays boundary layer separation. Investigations into tandem stators with various combinations of PP and AO show that the type of corner stall primarily correlates with changes of PP, and type of front blade corner stall first associates with wider operating range and lower losses. Considering both loss and stall margin, the optimal PP range for the tandem stator root is between 0.80 and 0.90, while the optimal AO range is between −0.05 and 0.