Current research has demonstrated the crucial role of spatial visualization skills in the Science, technology, engineering, and mathematics (STEM) related fields. Given the nationwide trend of the increasing population of university engineering students, more and more effort has been invested into how to effectively train students’ spatial visualization skills. In this study, we designed and developed a scalable online platform for training spatial visualization skills. Our online platform is capable of intelligent learning features such as individualized learning trajectory and personalized hints. In the current stage of the project, we deployed the online platform with over 600 university students. By analyzing student’s data, we identified a key question that has most predictive power on student’s spatial visualization skill. The promising result shows a bright future for an intelligent learning platform.