Cloud storage has become a major application model. As the number of users and data volume increase, cloud storage providers use deduplication technology to reserve storage space and resources. Existing solutions generally use a uniform popularity threshold to process all the data, while the issue is not addressed that different data information should have different privacy levels. A deduplication scheme is proposed based on threshold dynamic adjustment to ensure the security of uploaded data and related operations. The concept of ideal threshold is introduced, which can be used to eliminate the drawbacks of uniform threshold in the traditional schemes. The item response theory is adopted to determine the sensitivity of different data and their privacy scores, which ensures the applicability of data privacy scores, it can solve the problem that some users care little about privacy issues. A privacy score query and response mechanism are proposed based on data encryption. On this basis, the dynamic adjustment method of the popularity threshold is designed for data uploading. Experiment results and comparative analysis show that the proposed scheme based on threshold dynamic adjustment has sound scalability and solid practicability.