The invention discloses a double-faced automatic upper disk and lower disk weaving mechanism of an underwear 
machine and a pneumatic color spacing mechanism arm device. The double-faced automatic upper disk and lower disk weaving mechanism of the underwear 
machine and the pneumatic color spacing mechanism arm device comprise a needle disk base, a cutter disk base, a big-disk gear, a needle selector, a lower-section needle cylinder, a 
saddle base ring, an upper-section needle cylinder, a mechanical arm body, a 
yarn outlet mechanism pneumatic loop module and a 
yarn cutting mechanism pneumatic loop module. A needle disk is connected to the needle disk base. A cutter disk is connected to the cutter disk base. An air cylinder needle selecting device is connected to the cutter disk. The lower-section needle cylinder is connected to the big-disk gear. The needle selector is connected to the big-disk gear. The upper-section needle cylinder is connected to the lower-section needle cylinder. A reset triangle is connected to the 
saddle base ring. An automatic needle moving triangular mechanism is connected to the 
saddle base ring. An air inlet is formed in the mechanical arm body. The 
yarn outlet mechanism pneumatic loop module is connected to the upper end of the mechanical arm body. A yarn 
cutting mechanism pneumatic loop pipeline and a yarn 
cutting mechanism pipeline are communicated with the air inlet. The double-faced automatic upper disk and lower disk weaving mechanism of the underwear 
machine and the pneumatic color spacing mechanism arm device have the advantages of being simple in structure, convenient to operate and practical.