In recent years, copper nanoclusters (Cu NCs) have attracted a great deal of research interests, because the fluorescence intensity will be significantly enhanced after they aggregate, which makes them an ideal material for constructing chemical sensors. The current Cu NCs based sensor researches focus mainly on the control of surface modification and aggregation conditions. Herein, we report a method for direct detection of Cu2+ ions through in situ cluster formation and aggregation. Glutathione was used as both reducing agent and stabilizing agent, while tetrahydrofuran as the poor solvent. When the analyte of Cu2+ ions were added to the mixed solution, they were reduced and aggregated to generate bright orange emission. The method is easy to operate and the reaction complete within 2 min. The detection limit for Cu2+ ions is as low as 0.17 mu M. Based on these findings, we successfully achieved the determination of copper content in naturally occurring mineral. Therefore, the method reported here provides a convenient and sensitive way to perform qualitative analysis of Cu2+ ions.