The invention discloses an implementation method and a control device of selective blocking and deblocking of extra high voltage direct current transmission valve groups. When the valve groups of an inverter station (a rectifier station) are switched on according to a preferential blocking and deblocking function, the valve groups of the rectifier station (the inverter station) are switched on or off, and when communications are performed among stations, the inverter station (the rectifier station) selects high voltage valve groups or low voltage valve groups, to be switched on or off, according to the preferential blocking and deblocking function of the valve groups, and furthermore when no communication exits among the stations, the inverter station (the rectifier station) judges that one or more valve groups are switched off according to direct current bus voltage, and then selects the high voltage valve groups or the low voltage valve groups, to be switched on or off, according to the preferential blocking and deblocking function of the valve groups. The above preferential blocking and deblocking function of the valve groups is suitable for an extra high voltage direct current transmission running mode and an occasion which needs intersection blocking and deblocking in an overhaul, and specially suitable for the blocking and the deblocking of the valve groups, performed according to different demands of two alternating current grids when an extra high voltage direct current transmission layer is connected into the two alternating current grids.