Direct measurements of the optical absorption cross section (σ) and exciton lifetime are performed on a single silicon quantum dot fabricated by electron beam lithography (EBL), reactive ion etching (RIE) and oxidation. For this aim, single photon counting using, an avalanche photodiode detector (APD) is applied to record photoluminescence (PL) intensity traces under pulsed excitation. The PL decay is found to be of a mono-exponential character with a lifetime of 6.5 μs. By recording the photoluminescence rise time at different photon fluxes the absorption cross could be extracted yielding a value of 1.46×10-14cm2 under 405 nm excitation wavelength. The PL quantum efficiency is found to be about 9% for the specified single silicon quantum dot.