The time- resolved luminescence spectra of laser induced plasma from BaTiO3 were studied with a optical multichannel analyzer (OMA Ⅲ). The time-of-flight spectra of various particles, by which the concentration distribution of the responded particles was represented, were built by the emissive intensity of the same particles at different time. The spatial length of the ejected pulsed particle beam (i. e. plasma) was evaluated by the time-of-flight spectra, and the dependance of its dimension on the partial pressure range of buffer gas for laser deposition of oxides films with multielement was suggested, and the necessity of about 30 Pa oxygen partial pressure during laser deposition of high Tc superconducting films is explained.