This study aims to: 1) obtain data on the significance of the validity of the big book development product containing ethnoscience (The Process of Making Coconut Sugar in Purbalingga); 2) analyze the level of scientific literacy of fifth grade students before using the big book media containing ethnoscience (The Process of Making Coconut Sugar in Purbalingga); 3) analyzing the level of scientific literacy of fifth grade students after using the big book media containing ethnoscience (The Process of Making Coconut Sugar in Purbalingga). This study uses research and development methods with ten steps of research from Sugiyono. The subject of the product trial was 13 students and the usage trial was 42 students divided into a control class of 17 students and an experimental class of 25 students. Data collection techniques used a material and media expert validation questionnaire, student response questionnaires, teacher response questionnaires, student activity observation sheets, scientific literacy tests, documentation, and interviews. The data analysis technique uses qualitative and quantitative data analysis. The results showed that: 1) The data on the significance of the validity of the big book development product containing ethnoscience (The Process of Making Coconut Sugar in Purbalingga) from material and media experts showed a very valid category while the results of observations of student activities, teacher responses and student responses showed very strong categories; 2) The level of scientific literacy ability before using the big book containing ethnoscience (The Process of Making Coconut Sugar in Purbalingga) based on the N-Gain score shows a low category; 3) The level of scientific literacy ability after using a big book containing ethnoscience (The Process of Making Coconut Sugar in Purbalingga) based on the results of the t-test showed a significant difference in the increase in scientific literacy ability with the N-Gain score in the medium category.