The deformation behavior of headed studs is an important issue in the design of steel and concrete composite structures. In recent years, there is a rapid increase in the application of headed stud shear connectors in new types of concrete such as crumb rubber concrete and ultrahigh-performance concrete. In this article, totally 154 monotonic push-out tests from the literature on experiments of headed stud in various types of concrete were gathered and evaluated with the aim to study the deformation behavior of headed studs. As a result of a careful analysis on the effects of stud diameter and concrete properties on the shear stiffness of studs through the historic database, a new equation for shear stiffness was proposed. The new formula is a reasonably good predictor and is suitable for studs with a diameter ranging from 10 to 30 mm in the concrete with cylinder compressive strength ranging from 22.0 to 200.0 MPa. New formula for the load-slip curve of headed stud which includes a parameter related to the shear stiffness was also proposed. It can give good prediction for the slip not only at low load level but also large load level.