The invention relates to a hot air drying box, and belongs to the technical field of nonwoven machines. The hot air drying box comprises a box body, a hot air chamber and a combustion chamber which are arranged on two sides of the box body and are provided with fans, and two groups of hot air lead-out pipes which are arranged in a box body cavity. The hot air drying box is characterized in that each group comprises the same number of hot air lead-out pipes which are arranged at intervals to form upper and lower rows; a fabric guiding cavity is formed between the hot air lead-out pipes on the upper and lower rows; air outlet channels positioned on the hot air lead-out pipes on the upper row are downward, air outlet channels positioned on the hot air lead-out pipes on the lower row are upward, and the adjacent air outlet channels are partitioned by air flue partition pipes; each air flue partition pipe is contracted gradually towards the direction of pipe cavities of the hot air lead-out pipes and forms a structure of which the cross section is in a trapezoidal shape; and the widths of the air outlet channels are reduced towards the direction away from the pipe cavities from the pipe cavities. The hot air drying box has the advantages that an ideal hot drying effect can be achieved, the non-uniform heating phenomenon is avoided, large-thickness nonwoven fabrics or cotton fleecesare easy to penetrate, and the consumption of energy is reduced.