A new production method of spraying dextran-based polyurethane external splints is introduced in this paper. The main raw material components are polymethylene polyisocyanate (PAPI), mixed with surfactants, acetone, soluble starch, catalyst, and so on. The splint is used for temporary fixing after fracture, with small size, light weight, easy portability, fine air perviousness, completely transparent to the X-ray. It also needs a shorter fixed operating time. It can not only fix quickly and effectively the vertebral column and limbs, but also significantly shorten the time of pre-hospital care.