This study aims to describe the 3D model's online modules effectiveness in the practicing mastery of conceptual knowledge in solar system learning using an instrument which tested 58 7th-grade respondents from one of the junior high schools in Jombang, East Java, Indonesia. The respondents were then divided without randomization into 29 respondents for the experimental group (EG), which studied using 3D models online, and 29 respondents for the control group (CG), which studied using learning resources from student books and learning media in the form of 3D models from the NASA website. The effectiveness is assessed based on the results of the conceptual knowledge test instrument with the CRI method using a quantitative descriptive approach. Based on these results, the 3D models online module in solar system learning cannot be fully effective in the practicing mastery of conceptual knowledge. When examined further, 3D model's online modules are effective in cognitive dimensions C3, learning indicators 1, 2, and 6, and conceptual knowledge sub-types 1. Furthermore, based on research results, learning the solar system using online modules with 3D models is better than using the official NASA website with student books.