By the method of the experiment and the finite element, the production, development regulation and location of the plastic hinge of widened beam flange connections were studied. The test results showed good agreement with FEM results and proved the finite analysis reliable. The test specimens were designed as the base samples. By choosing some different main references relating to section shape change of widened beam flange connections, a series of finite element specimens which include eighteen direct arc widened beam flange connection and eighteen welded side-plate widened beam flange connections were derived from the base samples. The influence of widened beam flange depth, length and distance on plastic hinge distribution is discussed respectively, at the same time, the plastic hinge location range was given and practical section design method of widened beam flange connection is provided by revising the parameter of plastic hinge center location ls.