A method, device and system for reporting power headroom are provided, and the method includes the following steps: a user equipment determines whether it triggers power headroom reporting (PHR) (101); if triggering PHR, the user equipment reports power headroom independently or associatively basing on a component carrier (CC) or a power amplifier (PA) (102). The technical solution realizes power headroom reporting in a multi-carrier system by reporting power headroom independently or associatively basing on the CC or the PA, and can make a base station equipment process uplink scheduling better according to the power headroom coming from the user equipment.