Abstract: A diagnostic of time-resolved spectra of scattered light has been developed using optical multichannel analyzer coupled with optical scanning camera. The time-resolved spectra could achieve a goal of SRS temporal response with 10 ps resolution and dimensional response with 0.5 nm resolution. An experiment of laser-plasma interaction in hohlraum plasmas produced by laser beams with 351 nm wavelength, 1 ns pulse duration at SGⅡ laser facility is reported. The time-resolved spectra of scattered light by stimulated Raman scattering(SRS) were measured. There existed a delay-time for the Raman scattering corresponding to the entering laser. When laser entered into a smaller hohlraum, the delay-time was minished. Electron density was obtained by cut-off wavelength analysis.