Four edible oils and five oil-water ratios were heated to investigate the effect of water on the particle emission characteristics of particles emitted from heated cooking oil. PM2.5 and particles ranging from 0.01–10 μm emitted during oil-water heating were monitored via a DustTrak, a condensation particle counter and an aerodynamic particle sizer. The results showed that the PM2.5 levels and the particle number concentrations of the series of corn or peanut oil-water emulsions could be up to 6 and 50 times higher, respectively, than those of the series of soybean or canola oil-water emulsions. All heated oil-water emulsions at an oil-water ratio of 6-1 generated higher total particle concentrations than those of other ratios. The promoting factors (normalized by the corresponding oil volume to total volume) for the concentration of ultrafine particles, PM1 and PM2.5 ranging from 1.20 to 3.32, 1.14 to 2.50 and 0.71 to 2.14, respectively. In addition, the ratio of ultrafine particles (10–100 nm) to total particles and the particle number mode and median diameters changed with the oil-water ratio, but no obvious trend was observed. The regression results showed that the impact of water on particle emissions is not statistically significant.