It is enabled to conduct practicum in the Covid-19 pandemic learning, so that virtual laboratory was offered. Many virtual physics laboratory applications are offered, one of it is Golabz and Crocodile Physics. This research aims to design online physics learning about about RLC series circuit using Golabz which integrates Crocodile Physics and to investigate the effectivity of it towards students’ understanding. The research method used here is the development research with the ADDIE model (Analysis, Design, Development, Implementation, Evaluation). The online physics learning design based on inquiry learning about RLC series circuit using Golabz consists of three learning activities according to the learning objectives. Each learning has five steps, i.e. orientation, conceptualization, investigation, discussion, and conclusion. The research instruments are observation sheet, evaluation, questionairre, and validation sheet for the material and media. Based on the research above, the results of learning observation indicates that all respondents can follow the learning well with an average of 82% and gave positive responses to at least 70% of the statements with an average of 98%; some students were able to obtain evaluation results of more than 70% with an average of 71.88%. Thus, all indicators of success are achieved and the online physics learning design about RLCseries circuits using Golabz is said to be effective and sufficient to help students understand the material of RLC series circuits.