Chemical compatibility of sealing glass with metal interconnects is a critical issue for planar solid oxide fuel cell (SOFC). In this paper, interface reactions between a sealing glass and a ferritic metal interconnect (SS410) are tested under three different heat treatment conditions: sealing (static), aging (static), and thermal cycling (dynamic). The results show that the BaCrO4 crystals with two different morphology (round-shaped and needle-shaped) form both at the three-phase boundary (where air, glass, and SS410 meet) and on the surface of the sealing glass under the three conditions. Round-shaped BaCrO4 crystals form with low O2 concentration and short reaction time. Needle-shaped BaCrO4 crystals form with high O2 concentration and long reaction time. For the thermal cycling condition, the BaCrO4 formed at early stages causes the delamination of the sealing interface. Then, O2 diffuses into the interior interface along the delamination path, which results in the formation of BaCrO4 at the interior interface. The delamination-enhanced BaCrO4 formation during thermal cycling will lead to crack along the sealing interface, causing the striking increase of leak rates.