The microstructures and work-hardening behaviors of as-extruded and as-aged ZMT614-xY (x=0, 0.1, 0.5, 1.0) alloys were investigated by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and tensile test. The average grain size of as-extruded and as-aged ZMT614-xY (x=0, 0.1, 0.5, 1.0) alloys is decreased with more Y additive. A new irregular blocky MgSnY phase is formed when the content of Y reaches 1wt%. The work-hardening rate (θ) and work-hardening exponent (n) were obtained from the true stress-strain curves of as-extruded and as-aged samples. Due to the refined grains, the work-hardening rate θ of as-extruded and as-aged ZMT614-xY (x=0, 0.1, 0.5, 1.0) alloys are decreased with the content of Y increasing. Dynamic recovery of dislocations occurs during the plastic deformation, and the work-hardening rate θ of as-extruded and as-aged samples decreases as the deformation increases