Laser induced breakdown spectroscopy (LIBS) is a widely used material element detection technology. Because of its detection result is affected by many factors, and therefore, analysing and comparising the different experimental conditions have important significance for LIBS. Experimental sample produced by Beichuan County, Sichuan Province, China, which is ordinary Portland cement P.O42.5, using eight-channel fiber optic spectrometer AvaSpec-2048-USB2-RM, delay trigger DG645 for LIBS testing. Several metallic elements as Mg, Al, Na, K, which affect cement’s technical indicators were analyzed. Mainly compares the effect of laser frequency, the same point measurement times on different metal element spectral signal intensity, the optimum experimental parameters under the condition of this experiment: 10 Hz was the best laser frequency. When laser frequency is 10 Hz, the spectrum intensity of elements Mg, Al, Na, K were increased by 67.66%, 47.88%, 84.59%, 43.36% than 8 Hz. Because the tablet samples in place, the surface will have a small amount of oxidation and deliquescence, in order to measure 10 times for an average income results were recorded under the condition, with third, four records of results for the best.