Abstract: Using a set of aeronomical parameters,such as absorption cross sections for the dominant thermospheric constituents,EUV flux data from the Atmosphere Explorer Satellites and Hedin’s MSIS-87 neutral thermospheric model,the variations of penetration heights of solar EUV radiation with maximum and minimum solar activities are numerically calculated.For transmit-tance being l/e and 0.1/100,the variations of panetration height of EUV radiation in wavelength range 50-1050 A divided in 37 wavebands are also obtained.The results indicate the penetration heights are obviously controlled by solar activities,and the larger the transmittan-ce is,the closer the correlative relation of penetration height with solar activity is.At the solar zenith angles near normal astronomical sunset,the solar activity leads to increasing the penetration heights on one hand,and to decreasing the Chapman’s function,which reduces the penetration height on the other.These effects could physically explain some ionospheric phenomena observed at local sunset.