The influence of nature aging (NA) on the Portevin-Le Chatelive (PLC) effect was investigated via tension tests in solution treated 6061 Al alloy. The yielding strength, the tensile strength, the critical strain and the serration period changed little in the NA time range of 0~1 h and then increased with increasing NA time. The serration amplitude decreased in the NA time range of 0~2 h and kept constant over 2 h. The precipitation sequence of the alloy suggests that the precipitates that can significantly strengthen the alloy formed after NA for 1 h and increased linearly with NA time. These precipitates inhibit the dislocation motion and result in shortening the waiting time. It is more difficult to produce the pinning process and thus the serration period and the critical strain increase. Moreover, the solute atoms gather to mobile dislocations by body diffusion rather than pipe diffusion in this alloy.