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Split Hopkinson bar was used to study the dynamic mechanical properties of three tungsten heavy alloys (93W-4.9Ni-2.1Fe) with a wide range of strain rates (102~103 s-1) and temperatures (298~623 K), and the true stress-true strain curves can be obtained. The results reveal that fine-grained 93W-4.9Ni-2.1Fe-0.03%Y enters into the unstable plastic stage in advance, compared with other two 93W-4.9Ni-2.1Fe under the same conditions. According to experimental data, modified Johnson-Cook constitutive equations were fitted out and the fitting is better than the original Johnson-Cook model, with maximum relative error –3.4%. Comparing the constitutive parameters of three fine-grained tungsten heavy alloys, fine-grained tungsten alloy is considered to be possible to form adiabatic shear band (ASB).