The intensities of emission spectra of rusty iron plasma induced by Nd: YAG pluse laser, were experimentally studied in air atmosphere. Modified ME5000 echelle grating spectrometer coupled to intensified CCD camera was used to acquire the emission spectrum of laserinduced Fe plasma under the laser shock. The experimental results indicated that continuous laser impacts with certain energy were required to induce the Fe emission spectrum due to the existence of the impurities in the sample. The relative intensities of plasma spectra increased obviously after the impurities were decomposed during the process of laser shock. With the comparison of spectra acquired under 1st laser shock and in the cleaning process, it was shown that when the intensity of the characteristic line at the wavelength of 563.40 nm increased by 443.11%, the rusty iron was cleaned and the cleaningratio reached 99.84%. At the same time, the fluctuation of the spectrum decreased obviously during the cleaning. As a result, the changes of spectrum distribution and relative intensity of Fe spectrum lines could be used to judge whether the samples were cleaned or not through an analysis of the spectrum lines under 1st laser shock and those in the cleaning process.