As a kind of important means for DC frequency stability,frequency limit controller has been used widely in HVDC projects.DXB UHVDC project is faced with the problems of increasing frequency instability of the Yunnan power grid,as it runs asynchronously from the main grid,and the shortage of the opening unit in the initial stage of production.The configuration of FLC is very important.It analyzes two kinds of FLC control logic used in current DC project of China Southern Power Grid and compares the results of two kinds of control logic response through simulation test.The FLC configuration and parameter selection of DXB UHVDC are explained,and the response characteristics of FLC under the typical fault under the isolated island system are verified through simulation.And verify its function in DXB RTDS simulation platform as well as field test.