The rapid microwave synthesis and sintering of ZrNiSn bulk was studied in this work. The phase composition and microstructure of samples were characterized by using X-ray diffracmeter (XRD) and transmission electron microscope (TEM) technologies. The thermoelectric properties i.e. Seebeck coefficient (S), electrical resistivity (ρ), and thermal conductivity (κ) were measured through Seebeck coefficient/resistance analysis system (S/RAs) and laser flash thermal analyzer (LFT). The analysis results show that a relatively high purity single phase of ZrNiSn alloy was synthesized in merely 4~5min in microwave field, and small amount of impurity of Sn almost eliminated during 30min microwave sintering via secondary reaction. The variation trends of S, ρ and power factor with temperature were analyzed. The electrical resistivity was found has relative high value of 13.7~16.9μΩm. The highest power factor is 1683μWm-1K-2, lower than the previously reported, which should attribute to the high electrical resistivity. The thermal conductivity was decreased with temperature, and its maximum value is 4.288Wm-1K-1. The lattice thermal conductivity is merely 2.86~3.96 Wm-1K-1. The result of microstructure analysis shows that the growth of ZrNiSn grain was inhibited during microwave sintering. A large number of nanometer grains were precipitated in the interior of ZrNiSn grain and on the boundary. The calculated thermoelectric figure of merit (ZT) was found rapid increased with temperature, and a maximum ZT of 0.25 was achieved at 573~673K.