The invention relates to the technical field of turning processing, and discloses a hole drilling device for blades of a fan. The device comprises a rack, a hole drilling device and a working platform, wherein a groove is formed in the working platform, and a damage preventing hole is formed in the bottom part of the groove; compressing mechanisms, each comprising a driving part, a pressing plate,a supporting plate and a supporting shaft, are arranged on two inner sides of the groove; the supporting shafts are fixed to the bottom parts of the supporting plates and penetrate the bottom part ofthe working platform; elastic parts are arranged in the peripheries of the supporting shafts; an air box is arranged at the bottom part of the working platform; a piston plate is glidingly connectedinto the air box and is fixed to one supporting shaft; a reversing valve is fixed to the rack, and an air inlet of the reversing valve communicates with the damage preventing hole; one air outlet of the reversing valve communicates with the air box, and another air outlet of the reversing valve communicates with the air box; a connecting strip which slides along with the driving part is arranged on the working platform; and the connecting strip is connected to a valve element of the reversing valve. The device is simple in structure; and chippings can be treated during hole drilling and afterhole drilling of the blades of the fan.