The invention discloses a method for testing total power of omnidirectional radiation of an antenna by a GTEM cell, which comprises the steps of: placing an antenna of equipment to be tested on a three-dimensional non-metallic turntable in the GTEM cell first, determining the corresponding relation between various axes of local coordinates of the antenna of the equipment to be tested and various axes of coordinates of the GTEM cell, returning the reflection power of the antenna through a circulator, compensating the output power of a port of the GTEM cell by the reflection power of the antenna, and then calculating the total radiation power of the antenna of the equipment to be tested in a free space by a linear method or a TOP method. The method has simple operation and improves the accuracy of the test.