A lightning strike fault monitoring system for a wind turbine generator system and a lightning protection system (110) thereof, wherein the lightning strike fault monitoring system for the wind turbine generator system includes the lightning protection system. The lightning protection system (110) comprises a main body (101) provided with a blind hole (1011), a core (102), a connecting member (103) made of gasifiable material, a first elastic member (104), a second elastic member (105), a sealing cover (106), a bottom plate (107), and a switch used for connecting between an external signal source and a detecting terminal. The core (102) and the first elastic member (104) are respectively accommodated in the blind hole (1011), and the core (102) is connected to the main body through the connecting member (103). One end of the first elastic member (104) abuts against the core (102), and the other end is connected to the bottom wall of the blind hole (1011). One side of the sealing cover (106) is connected to the bottom plate (107) through the second elastic member (105), and the other side of the sealing cover (106) abuts against the core (102). The switch is mounted on the bottom plate (107). The lightning protection system (110) can accurately provide electrical signals for the detecting terminal, so that maintainer can be accurately aware of the occurrence of a lightning strike in order to perform maintenance and troubleshooting of lightning strike failure, thereby improving safety.