The accurate detection and quanti cation of nanoparticles (NPs) in aquatic environments are essential for toxicological and ecological risk assessment. Herein, we used single particle inductively coupled mass spectroscopy (SP-ICP-MS) to quantify titanium nanoparticles (Ti-NPs) in the extraction fractions of surface waters, and transmission electron microscopy coupled with an energy dispersive X-ray spectrometer (TEM-EDS) to specifically identify the nanoparticles. By using gold-NPs as reference standard, this approach achieved a Ti-NPs size detection limit in water of 25 nm with a particle number concentration limit of 10(2) particles/ml. We measured Ti-NPs concentrations in surface waters from Lake Taihu, China. The results revealed that the particles concentration was 2.78 x 10(5) particles/ml with the mean size of 67 nm in October 2016, and the particles concentration of 2.28 x 10(5) particles/ml with the mean size of 65 nm in April 2018, respectively. Based on TEM-EDS observation, various shapes of Ti-NPs were further identified, including regular cubes, long rods and flaky. We further measured the total organic carbon (TOC), and found that there was a positive correlation between Ti-NPs and TOC. This method enabled accurate detection and quantification of Ti-NPs concentration in environmental surface waters, which could be hugely useful for environmental risk assessment in aquatic systems.