Aluminum is most used material in 21st century in the world. Aluminum in used to sun block, aluminum cookware and even medicines. Aluminum is easily ionized in water via reaction with chlorides. Ionized Al3+ ions have harmful effects to human bodies such as Alzheimer's disease, Parkinson's disease and some neurodegerative diseases. So, it is very important to detect aluminum ions in water, before it accumulated in human body through food chain. The conventional method for detecting Al3+ ions have some limitations like a low sensitivity, harmful chemical composites and etc.... In this work, we present ultra-sensitive method for detecting Al3+ ion in water and real sample. By measuring the surface potential of Al3+/AuNP complexes, we detect Al3+ ions as low as 2 amol(1 pM, single droplet μL) in distilled water and 748 amol(374 pM, single droplet 2 μL) in drinking water which is boiled with aluminum foil and sodium chloride. The results shows that our method offer ultra-sensitive platform for detecting Al3+ in real samples.