The technological characteristics of Mg alloy in low pressure-expendable pattern casting were described. Following facts are shown: ( 1) the fluidity of molten metal in LP-EPC is affected by the flux and pressure of filling gas, casting temperature, coating thickness, foam density and vacuum level; (2) filling shape of molten metal in LP-EPC is presented in arch and layer forming from the in-gate on the condition of low filling velocity and low vacuum level, and filling shape would be more protuberant with high filling velocity, and attached wall effects are shown with high vacuum level. ; (3) the solidification of Mg alloy in LP-EPC advents the simultaneous solidification earlier compared with EPC; (4 ) mechanical properties of the Mg alloy in LP-EPC, such as tensile strength 180.8 MPa, yield strength 113.2 MPa, elongation 4.4%, are superior to those in EPC and in resin sand casting, and equivalent to that in metal mold casting, which can meet the performance requirements of die casting Mg alloy after heat treatment. Production verifies that Mg alloy in LP-EPC has the advantages of good anti-oxidation ability, excellent fillingperformance and mechanical properties, and can produce high precision and thin-walled complex components.