The invention discloses a microwave millimeter wave ultra-wide band low phase shift six-figure attenuator formed by cascading a 0.5dB attenuation unit, a 1dB attenuation unit, a 2dB attenuation unit, a 4dB attenuation unit, a 8dB attenuation unit and a 16dB attenuation unit, wherein the 0.5dB attenuation unit and the 1dB attenuation units are in T-shaped topological structures; the 2dB attenuation unit and the 4dB attenuation units are in an n-shaped topological structures; the 8dB attenuation unit is in a structured formed by cascading two n-shaped topological structures; the 16dB attenuation unit is in a switched topological structure; the 2dB attenuation unit, the 0.5dB attenuation unit, the 16dB attenuation unit, the 1dB attenuation unit, the 8dB attenuation unit and the 4 dB attenuation unit are in cascade connection in sequence; the work frequency range of the attenuator is 2-18GHz; and 64 attenuation states can be realized within the attenuation range of 0.5-31.5dB by taking 0.5dB as a stepping value. The attenuator has the advantages of simple circuit topological structure, simpleness and convenience for design, low process difficulty, low inserting loss, small phase shift and high attenuation precision for various attenuation states, small standing wave ratio of the input end voltage to the output end voltage, wide working band, small circuit size, simpleness for control and convenience for use and is convenient for large-batch production by adopting a microwave singlechip integrated circuit process technology.