The ion flow field (including the total electric field and ion flow density) is an important electro-magnetic environmental factor for the design and operation of ultra high-voltage direct-current (HVDC) transmission lines. Because the overhead lines are long and pass different altitude, humidity and air quality regions, the ion flow field can be influenced by external meteorological factors such as air pressure, humidity and particulate matter, which makes the modeling and analysis of ion flow field complicated. This paper reviews the literature on the characteristics of ion flow field of HVDC transimssion lines, and analyzes the effects of altitude, humidity and particles on the ion flow field characteristics, and finally clearly points out the existing problems in the current research and the future research prospects, and are helpful to the modelling and characteristic analysis of ion flow field of HVDC transmission lines in high altitude, high humidity and high pollution areas.