Transformation. The idea of transformation mathematics is used to calculate the volume of cobblestones, and a simple method to calculate the volume of irregular objects is explored and mastered, thus realizing the diversity of problem-solving strategies. By exploring and measuring the volume of irregular objects, we can further understand the application of the mathematical thought of "reduction" in solving problems. Further cultivate students' ability to analyze and solve problems intuitively with the help of geometry. Using the mathematical thinking method of "transformation" to find the volume of simple irregular objects. The volume of pebbles can be calculated by drainage method.