This document describes the design of a cloud-based mobile social TV system called CloudMoV. CloudMoV allows mobile users to stream live or on-demand videos from various sources and watch them together while chatting. It utilizes cloud computing services like IaaS and PaaS to offer high quality video streaming by encoding videos at different formats and bitrates. The system architecture includes modules like transcoder, reshaper, social cloud and messenger to enable synchronized video viewing and messaging between users. The authors implemented a prototype of CloudMoV on the Amazon EC2 platform and evaluated its performance.