A brief overview of the results of the investigations of the red giant star Arcturus is given . One-dimensional LTE modeling of the atmospheres of Arcturus and the Sun as a star is carried out on the basis of synthesis of the extended wings of the H and K Ca II lines . It is found that the local continuum in this spectral region is underestimated by an average of 12 % in the atlases of Arcturus . The average deficit in UV absorption amounts to 43 % for Arcturus whereas it is 9 % for the Sun . For Arcturus the correction factor to the continuum opacity at the wavelengths of 390.0 , 392.5 , 395.0 , 398.0 , and 400.0 nm equals 2.20 , 1.90 , 1.70 , 1.55 , and 1.45 . The model atmosphere of Arcturus obtained from the best-fit of the wings of the H and K Ca II lines corresponds to the model atmosphere with the fundamental parameters T _ { eff } = 4286  K , \log g = 1.66 , and [ Fe/H ] = - 0.52 derived by Ramirez and Allende Prieto ( 2011 ) . The temperature stratification of Arcturus ’ atmosphere is presented in tabular form . To obtain more accurate temperature stratification in the future , we need a high spectral resolution spectrum calibrated to absolute fluxes with high accuracy .