Provided are a method, apparatus and system for measuring total radiated power of an array antenna. The method includes: determining a Rayleigh resolution of the array antenna in an angle space, and setting a stepping grid spacing of sampling points according to the Rayleigh resolution; determining the sampling points according to the stepping grid spacing, measuring equivalent isotropic radiated power (EIRP) at positions of the sampling points and determining the TRP according to the EIRP. Compared with a traditional rest mode using an angle stepping grid θgrid and φgrid of 15°, this reduces measurement errors; and additionally, through a normalized wave vector space transformation, the number of sampling points is further reduced, and the measurement efficiency is improved.