Nickel oxalate dihydrate (NiC₂O₄·2H₂O) was prepared by coprecipitation method using nickel nitrate and oxalic acid as the raw materials. The product was characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),laser granularity measurement device,elemental analysis,Fourier transform infrared (FT-IR) spectrometry and TG-DTG analysis. Its catalytic effect on the thermal decomposition of TEGDN/NC propellant was studied via thermogravimetry-mass (TG-MS) coupling technique. The results show that the product contains crystal water,and its molecular formula is NiC₂O₄·2H₂O. The product has good dispersion and its average particle size is 15.97 μm. NiC₂O₄·2H₂O loses crystal water at the range of 180-250 ℃ and then decomposes at higher temperature. TG-MS analysis shows that adding 2% NiC₂O₄·2H₂O can accelerate the thermal decomposition of TEGDN/NC propellant and accelerate the generation of gaseous products. The integral intensities of ion currents were calculated,and it is found that the generation amount of HCHO is obviously increased during the thermal decomposition process.