Improving the intensity of laser-induced plasma emission spectrum is of great significance for enhancing the measuring accuracy of weak spectral signal and improving the detection sensitivity of low content elements in analysis material. The metal sample was heated in the first and ablated by the Nd:YAG nanosecond pulse laser with the wavelength of 1 064 nm in the air under the certain temperature. The plasma was produced. Then the line intensity and signal-to-noise ratio of spectrum were measured under the different sample temperature. The results show that, with the increase of sample temperature under the condition of laser energy for 200 mJ, plasma radiation increases and reaches the maxmum at the sample temperature of 150 ℃. Calculations show that the spectral line intensities of Mo, Cr, Ni and Mn increases by 54.56%, 72.43%, 70.29% and 54.01% respectively, and the spectral signal-to- noise ratios increases by 37.44%, 40.74%, 38.6% and 37.06% respectively compared with that of the room temperature. By observing the plasma images and measuring the temperature of the plasma, electron density and the sampleevaporation, the cause of the radiation enhancement of laser-induced metal plasma was discussed. Visibly, the rise of the sample temperature is a effective method for enhancing the quality of the laser spectrum.