THz wave emission from ZnTe nano-colloidal aqueous dispersion flow (the particle size is 5-nm in diameter, the flow thickness is 17 mu m) with two different particle densities (1.60 mmol/L and 1.07mmol/L) was measured by time-domain spectroscopy (TDS) under femtosecond laser irradiation (>35 fs/transform-limited, 800 nm, horizontally-polarized, 0.5 kHz) in air. Intensity increase and peak shift in the TDS signal wave-form if compared with distilled water indicate that THz wave emission is induced in ZnTe nano-particles in the aqueous dispersion.