The invention discloses a subsynchronous oscillation monitoring protection apparatus and a subsynchronous oscillation monitoring protection method. According to the apparatus, oscillation frequency is obtained by performing online recognition on subsynchronous oscillation signals in instantaneous power on each current collection line in a new energy station, and each collecting inlet line and outlet line in a new energy collection station; then voltage and current subsynchronous/super-synchronous components in each line are extracted through filtering design; three kinds of protection elements for performing subsynchronous/super-synchronous oscillation impedance protection, subsynchronous/super-synchronous harmonic current protection and subsynchronous power oscillation protection are further provided specific to the extracted subsynchronous/super-synchronous components, wherein the subsynchronous/super-synchronous oscillation impedance protection is main protection; the subsynchronous/super-synchronous harmonic current protection and the subsynchronous power oscillation protection are backup protection; and therefore, the apparatus can perform protection to rapidly cut off a disturbance source in subsynchronous oscillation so as to safeguard safe and stable operation of the system.