Computation of bridge structures is an important specialized course for senior students majoring in bridge engineering, which is of great significance to the cultivation of students’ ability to solve complex engineering problems. Understanding boundary conditions has always been a key and difficult point in teaching. In order to help students to understand boundary conditions quickly, a teaching exploration integrating with structural mechanics is carried out based on the eighty five percent rule for optimal learning. Four groups of questions are set up based on the construction drawing of an actual continuous beam bridge. The boundary conditions are combined with the known knowledge of kinematic analysis and rods, leading to four gradually deepened levels of understanding about boundary conditions. These explorations enable students to dialectically understand the classification of boundary conditions, the relationship between imposing (removing) constraints and rods, the relationship between boundary conditions and geometric models, and the meshing of the finite element model. Using the idea that not only all boundaries are connections, but also all nodes (sections) are connections, the supports and all kinds of connections in MIDAS/Civil are represented by chain bars. The relationship between six degrees of freedom constraint directions and six chain bars is given, laying a foundation for students’ subsequent software operation. The teaching practice in the past five years shows that the problem-oriented teaching method of computation of bridge structures based on the eighty five percent rule has a good effect, and students rarely make mistakes in confusing different types of boundary conditions in the subsequent computer modeling.