In today's Business world, big data projects play an important role in increasing the profit of the business. Success of the big data project lies on the complete understanding of the customer requirement. A big data project not only gives the solution for day to day functionality of the system but also gives a solution to improve the business. Hence understanding the requirement is very important. Most of the big data projects are based on the object oriented approach. Most of the software industry relies on UML use case model to specify, analyze and design the big data project. The difference between other project and big data project is data characteristics. The three V characters, volume, velocity and variety play major role in the design decision of big data project. The existing UML use case diagram does not have a facility to represent the big data V characteristics. In this paper we are proposing big data use case diagram, suitable for specifying big data characteristics. The research result shows that big data use case diagram improves the understandability for the requirements of the big data project. © 2019 American Scientific Publishers.