Abstract: The relationship between the martensite content and the mechanical property of 304 stainless steel was investigated through uniaxial tensile tests by changing strain rate. When the strain rate increased from 3×10^-3 s^-1 to 3×10^-1 s^-1 at the room temperature, the yield strength increased from 220 to 370 MPa, while the tensile strength and ductility decreased from 1260 to 1000 MPa and from 57% to 42%, respectively. While the volume fraction of sample martensite dropped from 55% to 21%. The results indicate that the steel's plasticity is closely related to the martensite content, suggesting that the dominant deformation mechanism of the 304 stainless steel can be attributed to strain-induced martensitic transformation.