Abstract: In order to improve the spacial resolution of ionospheric virtual height in vertical ionospheric sounding, a high precision virtual height measurement experiment are carried out by means of ionospheric echo＇s phase measurement and corresponding data analysis processing arithmetic with modern digital ionosonde. When two radio frequency pulse signals, the frequency difference of which is a fixed value are transmitted and the echo＇s phase difference is measured, the ionospheric virtual height with high precision can be acquired. According to this ionospheric virtual height sounding principle, the observation mode of ionospheric virtual height with high precision is realized. In this mode, the measured height resolution of the ionospheric virtual height is increased by more than ten times, that is, from 6 km to about 200 m, which can entirely satisfy the observation research demand of the ionospheric fine structure and small scale disturbances. Through a series of virtual height measurement experiments by using combinational pulses control and echo＇s phase measurement analysis based on CADI ionosonde, some meaningful results are obtained and some comparisons are made with TOA （Time Of Arrival） method. Experimental results reveal that the height resolution of ionospheric virtual height measurement with echo＇s phase method is ten times higher than that of virtual height measurement with TOA method. This is very important in that electron density profile under ionospheric peak can be accurately inversed and ionospheric fine structure can be carefully studied.