Disclosed is a drilling tool 
assembly used for directional hole-forming underground a 
coal mine and provided with an air screw motor and construction method. The drilling tool 
assembly comprises a directional 
drill bit, the air screw motor, a lower non-magnetic 
drill rod, a 
wireless electromagnetic wave 
measurement while drilling short section, an upper non-magnetic 
drill rod, a middle drill rod and a blower which are connected in sequence. The drilling tool 
assembly can carry out composite drilling and sliding 
directional drilling for construction: when composite drilling is conducted, the air screw motor drives the directional 
drill bit to crush rocks in rotatably, meanwhile, the middle drill rod rotates to drive the air screw motor to rotate, boring mud at the bottom of a hole is discharged from the bottom of the hole by 
compressed air along an annular gap, and the middle drill rod can be used for auxiliary slagging; and when sliding 
directional drilling is conducted, the middle drill rod does not rotate, the directional 
drill bit is driven by the air screw motor driven by the 
compressed air to rotate to crush rocks, and the track of the hole is controlled by changing the 
elbow orientation of the air screw motor. Thus, according to the drilling tool assembly used for directional hole-forming underground the 
coal mine and provided with the air screw motor and construction method, the drilling depth of a soft 
coal seam and the coal seam drilling-encounter rate can be improved greatly, and the drilling gas extraction effect is improved.