The invention discloses a traffic speed measuring radar for an expressway. The traffic speed measuring radar comprises a radio frequency unit, wherein a radio frequency source for transmitting a signal and a receiving antenna for receiving the signal are arranged in the radio frequency unit; the radio frequency unit is connected with a main control unit through an analog-to-digital converter; a digital processing module for processing the signal to obtain a target speed is arranged in the main control unit; the receiving antenna comprises an array phase plate formed by arranging more than twophase shifting units; each phase shifting unit comprises a dielectric layer; a copper rod with a double-helix structure is arranged on the back of each dielectric layer; and a metal patch layer is arranged on the top surface of each dielectric layer. The traffic speed measuring radar has a very excellent incident wave receiving and focusing effect and high incident wave receiving capacity, and hasvery high absorption rate; and absorption of incident waves reaches ultra-wideband absorption.