The invention provides a T-shaped air duct cooling device applying trapezoid cooling fins. The T-shaped air duct cooling device comprises a shell, a cubic
heat sink, an L-shaped square
pipe and an air suction fan, wherein the cubic
heat sink is a hollow cuboid, air inlets are arranged at two axial ends, an air outlet is formed in a side wall, a plurality of trapezoid cooling fins are fixedly arranged on two side walls, opposite and perpendicular to the air outlet, of an inner cavity of the trapezoid cooling fins and are arranged uniformly, a rectangular plate is arranged at one segment, perpendicularly facing the air outlet, of each trapezoid cooling fin, a
right trapezoid plate is arranged at one segment parallel to the air outlet, an upper bottom edge of the
right trapezoid plate perpendicularly faces the air inlet near to the rectangular plate, the air outlet is communicated with the air suction fan through the L-shaped square
pipe, T / R modules are arranged at outer sides, fixedly connected with the trapezoid cooling fins, of two side walls, and the T / R modules are sealed between the air inlets and the air outlet of the
heat sink. The T-shaped air duct cooling device has the advantages of simplicity in structure, small size, light weight and balanced
cooling effect, and is easy to process, and the three-protection requirement of an
active phased array radar can be met.