Influence of homogenization on mechanical properties of Al-1Mn-1Mg alloy prepared by different melttreatments was discussed and mechanism of metallurgical defects on ingots' mechanical properties was analyzed. It was found that metallurgical defects, such as the inclusions and gas holes, cannot be removed from the original ingots by homogenization; the average increasement of tensile strength of the ingots prepared by comprehensive melt-treatment and homogenized at 400~500°C for 12 hours was 17.4%, and the elongation improved slightly; the better obdurability of the ingots can be obtained due to the vast reduction of crack initiation of metallurgical defects such as the inclusions, gas holes and so on; the fracture mode gave priority to the type of transcrystalline and micropore gathering; under the experiment condition, the relatively optimized processing permanents of homogenization can be obtained by heating at 450~500°C while holding for 12 hours and air cooling; the comprehensive mechanical properties of the ingots, prepared by the optimized process, can be tested as follows: b 180~193MPa, 16.0~18.0%..