Polar Mesosphere Summer Echoes (PMSEs) are very strong radar echoes in polar mesopause at local summer. This paper presents the frequency dependence of volume reflectivity and the effect of energetic particle precipitation on modulated PMSE, by using the PMSE observations carried out simultaneously with European Incoherent SCATter (EISCAT) Very high frequency (VHF) and Ultra High Frequency (UHF) radars on 12 July 2007. Based on experimental observations, the PMSE occurrence rate at VHF is much higher than that of UHF, and the altitude of the PMSE maximum observed at VHF is higher than that at UHF. There are overlapping regions between the high-energetic particle precipitation and the PMSE observed by the VHF radar. Also, the high frequency (HF) heating has a very limited impact on PMSE when the UHF electron density is enhanced due to particle precipitation. At the same time, an updated qualitative method is used to study the relation between volume reflectivity and frequency. It is found that the volume reflectivity is inversely proportional to the fourth power of radar frequency. The theoretical and experimental results provided definitive data foundation for further analysis and investigation of the physical mechanism of PMSE.