The invention provides a hot air oven with an adjustable upper air flue, belonging to the technical field of a non-woven machine. The hot air oven comprises an air flue frame, an upper air flue arranged at the upper part of the air flue frame, and a lower air flue arranged at the lower part, wherein an air outlet is arranged at the bottom of the upper air flue and an air returning hole is arranged at the top of the lower air flue; the hot air oven is characterized by further comprising an upper air flue hoisting mechanism, a power transmission mechanism, a first upper air flue hoisting beam and a second upper air flue hoisting beam; the upper air flue hoisting mechanism is arranged at the top of the air flue frame and the power transmission mechanism is arranged at the top of the upper air flue and is connected with the upper air flue hoisting mechanism; the first upper air flue hoisting beam is arranged at one side of the upper air flue and is hinged with one side of the air flue frame and is connected with the upper air flue hoisting mechanism; and the second upper air flue hoisting beam is arranged on the other side of the upper air flue, is hinged with the other side of the air flue frame and is connected with the upper air flue hoisting mechanism. The hot air oven has the advantage that the upper air flue can be hoisted or descended aiming at non-woven textiles or cotton nets with different weights, so as to improve the use adaptability and be good for saving energy sources.