As the energy source of the chemical oxygen iodine laser (COIL) the singlet oxygen generator (SOG) is a key part of the COIL, and consequently, the concentration of O2(1Δ) and water vapor is two important parameters for the SOG. The concentration of water vapor is another important parameter for the SOG because water can strongly quench I* which is the luminesent medium of COIL. It is a difficult problem how to measure the two parameters easily and accurately. The piston source method has been used to measure the absolute concentration of O2(1Δ) and water vapor in a jet-type SOG. Some curves about the O2(1Δ) yield and water vapor concentration also has been given. The change law of the varions parameters is given from a quantity of experimental results. These results offer references for studying the jet-SOG.