A method, based on ultra-wideband technologies, is designed to quickly measure the phase-shifting steps of phased-array antenna element which is inconvenient to demount. By coupling and feeding UWB signals in picoseconds to antenna elements, phase-shifting steps of antenna element can be tested according to sampling echo signals. The use of data processing algorithms, such as window function method, greatly improves the accuracy of the test. A time domain measurement system of UWB used for testing phase-shifting steps of some phased-array antenna element is set up. The simulation is good in agreement with practice, and demonstrates the feasibility of the method in engineering practice.