The effects of disproportioned hydrogen pressure, dehydrogenation recombination temperature, dehydrogenation recombination vacuum degree and addition of alloying element Co on the magnetic properties of Nd12.5Fe80.4-xCox Ga0.5 Zr0.1B6.5 (x=0,4,8,12,15,17,20) alloys in d-HDDR process were studied. The phase structure of magnetic particles was characterized by X-ray diffraction (XRD). The results show that the phase transition process of the alloy in the d-HDDR process is: Nd2(Fe,Co)14B+2H2<=>2NdH2+12a-(Fe,Co)+(Fe,Co)2B; The disproportioned hydrogen pressure below 0.025 MPa is the key to the magnetic anisotropy generated by NdFeB magnetic powder, and the system of combining high temperature, low vacuum and high vacuum in the dehydrogenation and recombination stage is the guarantee of high anisotropy of NdFeB magnetic powder. When the disproportioned hydrogen pressure was 0.025 MPa and the dehydrogenation recombination temperature was 840 °C, the anisotropic DOA value of magnetic powder was 0.74. The addition of alloying element Co is beneficial to improve the coercivity and anisotropy of magnetic powder, and when the Co content is 15 at% (atomic fraction), the alloy obtains high comprehensive magnetic properties after the best treatment process: DOA=0.62, Br=1.27T, jHc=754.3 kA/m, (BH)max=245.7 kJ/m3.