The invention discloses a black start system for a wind power plant. The black start system comprises a wind power generator group, an energy storage power supply for supplying a start power supply to the start of the black start system, a flexible alternating-current power transmission device and a master control unit, wherein the wind power generator group comprises N wind power generators which are connected in parallel; one end of each wind power generator is respectively connected with an outlet circuit breaker; each outlet circuit breaker is connected to a busbar of the wind power plant in parallel, and the other end of each wind power generator is connected with each of the corresponding N local monitoring units; the flexible alternating-current power transmission device is connected to the busbar of the wind power plant in parallel; the master control unit is used for carrying out real-time bidirectional communication with the energy storage power supply, the flexible alternating-current power transmission device and the local monitoring units respectively through signal busbars. The invention also discloses a method for black start of the wind power plant. According to the black start system and the method disclosed by the invention, under the condition that the wind power plant is completely powered off and does not rely on an external power grid, self-starting of the wind power plant is realized, a starting sequence of fans can be optimized according to real-time wind velocity conditions, and thus economic and fast effects of a black start process are achieved.