X-ray loud M dwarfs are a major source of by-products (contamination)in the X-ray band of the multiwavelength quasar survey.As a by-product,the low dispersion spectra of 22 M dwarfs are obtained in which the spectra of 16 sources are taken for the first time.The spectral types and distances of the sample arc given based on spectral indices CaH2,CaH3,and TiOS.The parameter (ι)TiO/CaH is calculated to separate the different metallicity classes among dwarfs,subdwarfs and extreme subdwarfs.We also discuss the distributions in the diagrams of log( Lx/ Lbol),the ratio between X-ray and bolometric luminosity versus spectral type and infrared colors.