[en] A method for superposing spectroscopy was developed and it can inquire simultaneously any energy span α spectroscopy of radon progeny and thoron progeny for any period. When measurement period was overlapped in an optimized α spectrum method for measuring radon progeny concentration and thoron progeny concentration in air the spectrum superposition method resolves this problem. So it can measure quickly and reliably radon progeny concentration and thoron progeny concentration in air on the ORTEC α spectroscopy workstation. (authors)