With the large-scale development of wind power, it increases rapidly the number of directly-driven permanent magnet wind turbines connected to the grid, thus which threatens the safety and stability of operation in the power grid. The low voltage ride-through (LVRT) is the primary problem in terms of the safety of wind power connected to grid. The corresponding strategies for wind farms with directly-driven permanent magnet synchronous generator (D-PMSG) are provided from the present researches of LVRT technology for traditional wind farms and other new energy power plants. A review of mainstream LVRT technologies suitable for the features of wind farms with D-PMSG is reported. The mechanism and application of each technology are introduced. The advantages and disadvantages of different technologies are compared, and then corresponding suggestion on the future application is given out. The trend of LVRT technology is discussed. The economic and technical challenges for current large-scale grid-connected wind farms are pointed out for further research.