The microstructures and kinetic characteristics have been studied during heat treatment of AM60B alloy prepared by thixoforming. The results indicate that primary particles and secondary grains coarsened rapidly in initial 1 h solution treated at 430°C, and then slowed down. Their growth modes were different in the initial 1 h and then turned to be same. Accordingly, the alloy hardness dropped quickly before 1 h. Ageing hardness depends on both content of precipitates and the morphology. Adding content of the precipitates hardened the alloy till 8 h aged at 215°C after 24 h solution treatment at 430°C, and then the precipitates coarsening weakened the ally.