The purpose of this study was to determine the effectiveness of the use of online 3-dimensional poster media on Google Classroom-based solar system material in order to improve understanding of the physics concepts of class VII students of SMPN 1 WERA. This research is in the form of true experimental research of pre-test and post-test. The study population was the VII grade students of SMPN 1 WERA located in Tawali Village, Kec. Wera, Kab. Bima, NTB. The lessons used are those that do not use online 3-dimensional poster media for the control class, for the experimental class using 3-dimensional poster media online. The research sample was class VII-1 as the experimental class and class VII-2 as the control class. There are three stages of data collection techniques, namely the preparation stage, the stage of determining the initial capacity of the sample, and the stage of implementing the action. The research instrument was an objective test, namely the validity test, the reliability test, the difficulty level test, and the discriminating power test. The data analysis technique used is the analysis requirements test including the homogeneity test and normality test. As well as hypothesis testing in the form of t-test. Obtained the results of t-test calculations, pre-test t = 0.332 and t table = 1.682 (t count <t table). It means that the null hypothesis (Ho) is accepted and the alternative hypothesis (Ha) is rejected. This indicates that there is no difference in students' initial abilities. The post-test value t = 2.744 and t table = 1.682 (tcount> ttable) means (Ho) is rejected and (Ha) is accepted. The results of the analysis of the N-gain test value; the experimental class was 0.44 in the "medium" category and the control class was 0.22 in the "low" category. Finally, it was found that the effectiveness of using online 3-dimensional Media Posters on Google Classroom-Based Solar System Material can improve understanding of the physics concepts of Class VII students of SMPN 1 WERA in the 2019/2020 academic year.