The Covid-19 pandemic has had a significant impact in the field of education, one of which is the implementation of online learning policies. In online learning, teaching materials are needed to facilitate students to learn and develop themselves to achieve competencies according to course objectives. In the science class subject, discovery learning is very important to improve students’ critical thinking skills. This study aims to develop a module based on discovery learning approach to improve critical thinking skills in the digestive system and nutrition in the basic concepts of science subject, majoring in primary school teacher education, Faculty of Education, UNNES. Module with discovery learning development based on the Ministry of Education development model that adapted from Borg and Gall procedure development through some steps: (1) doing product development analysis, (2) developing beginning product, (3) expert's validation and revision, (4) small-scale field test and product revision, and (5) significant scale field test and last product. The research results showed that the quality of the product in validation aspect fulfill very good criteria based on the mark from a material expert, media expert, and students. This module was proven to improving students' critical thinking skills.