Abstract: Solar eruptions, such as flares and coronal mass ejections, are the major drivers of space weather between the Sun and the planets. Therefore, understanding the mechanism of solar eruption and further predicting solar eruption is an important prerequisite for the accurate and quantitative forecast of space weather. Although it has been well recognized that solar eruptions originate from the complex structure and evolution of the coronal magnetic field, the underlying physical mechanisms remain elusive. The key to studying the coronal magnetic field associated with solar eruption is to obtain the three-dimensional (3D) coronal magnetic field. Due to the difficulty of directly measuring the solar coronal magnetic field, physical models with numerical implementation and constrained by the photospheric magnetogram have been developed. The model statically reconstructs the three-dimensional coronal magnetic field with a single magnetogram snapshot and dynamically simulates the coronal magnetic field with a time series of magnetograms. We review the progress made during the last decade in studying the three-dimensional complex magnetic structure of the corona in solar eruptions, including the development of new coronal magnetic field extrapolation methods and a data-driven coronal evolution model based on time-series vector magnetograms. During the eruption, the complex magnetic topological properties and their evolutionary components are investigated. Finally, a comprehensive discussion of the eruption mechanism is investigated in conjunction with observations and simulations. These advanced techniques of coronal magnetic field modeling have played an important role in characterizing the formation and evolution of the complex coronal magnetic field and revealing the physical mechanism of the eruptions. Such new techniques can track the generation process of the coronal magnetic flux rope. Alternatively, they can be used to analyze the specific role of photospheric motion in creating the magnetic flux rope and diagnose their instability. The new simulation techniques can also realistically reproduce the magnetic field evolution during an outburst. By in-depth analysis of magnetic topology and evolution combined with observation and simulation, these studies have significantly improved our knowledge of the complexity of the 3D coronal magnetic field and will continue to refresh our understanding of the mechanism of solar eruptions.