According to the experimental results of spectrum diagnosis made on Qiang-Guang-I generator, we report a method to separate and diagnose Z-pinch plasma radiation spectrum. Spectral lines and different continuums are separated from experimental results and electron temperatures can be acquired. Results show that continuums are superposed by radiation of high electron temperature plasma at the centre field (Te=290.7 eV ± 1.2 eV) and radiation of lower electron temperature plasma at shell region (Te=95.3 eV ± 8.3 eV). Spectral lines reflect the information of high electron temperature plasma at the centre field. According to the calculation by using NLTE model, the electron temperature of such a plasma is in the range of 299–313 eV. The diagnose result by spectral lines is identical with the continuum's results.