Lack of understanding of the concepts measuring units of length can cause students difficulties in measuring objects, determining the right measuring instrument, finding relationships between standard units of length, and applying the concept of measuring units of length in everyday life. This study aims to develop Discovery Learning-Based LKPD as an effort to increase students' understanding of concepts, especially in the material of unit length measurement. This research was carried out using the Design and Development (D&D) method with the PPE (Product Development) development model. This model consists of three steps, namely 1) Planning, 2) Production, and 3) Evaluation. The data collection technique used is a questionnaire. Data analysis technique used quantitative data using a Likert scale. The results showed that the LKPD Based on Discovery Learning on unit length material was included in the very feasible criteria for use with a proportion of 92% according to material experts, 86% according to learning practitioners, 100% according to media experts and 99% according to students' responses. The conclusion of this research is that the Discovery Learning-Based LKPD on Unit Length Measurement material is appropriate to be used to help students understand the Length Unit Measurement material in grade 3 SD.