Aluminium alloy (Al) 6061 become one of the most significant electrical components due to its conductivity performance. House moving contact resistor of circuit breaker in power system is one of the application of this alloy. However, in the manufacturing process, Al 6061 often fails meet the mechanical property and conductivity requirements. The properties of Al 6061 can be improved by treating the alloy with heat to facilitate natural aging or artificial aging. In order to provide data and evaluate the effect of heat treatment, specimens were observed through different holding time and quench media in this research. Specimens were heated to 536oC in a muffle furnace in order to surpass the solidus line and undergo a single phase. To conduct fast cooling after heating and holding it for some time, water was used to perform quenching. The holding temperature of tempering after solution treatment was maintained by putting specimens in room temperature for 1, 2, and 3 months to age naturally. As a comparison, other specimens were heated in a furnace and held for 15, 18 and 21 hours to allow artificial aging. The results confirmed the important role of heat treatment in microstructure and properties. The formation of Mg2Si precipitates was found which increased tensile strength, hardness, and conductivity. The formation of Mg2Si was influenced by the holding time in the aging process. The longer aging time, the bigger the precipitates.