The article first analyzes the big data transaction background, significance, basic principles and characteristics, think big data transaction shall follow the principle of party autonomy, rights run out and the principle of power restriction, big data deal with object invisibility mark, right main body and the diversity of trade, etc. On this basis, the preliminary analysis on big data transaction legal risk, think big data trading activity was still in the stage of commercial practice, the main body of large data transaction, mark, risk-taking, right relief, etc., still are certain aspects of the lack of legal basis, no specific legal risks are widespread. Put forward, according to the principle of "autonomy", through the contract way to control legal risks, such as participation and promote the formulation of the relevant laws and regulations and standard data, take measures necessary to explore the large data such as trading legal risk control countermeasures.