Recently, multiple parties cooperate together in online collaborative systems, e.g., Overleaf and Git, to enhance working efficiency, while with concerns about losing ownership of their online dynamic data. For traditional cloud storage services, the dynamic provable data possession (DPDP) schemes work well in ownership validation over dynamic data. However, DPDP may compromise privacy in such multi-party setting due to no anonymous in underlying cryptographic primitives. Considering potential ownership abuse from participants, linkable ring signature seems promising to provide tractable anonymous. Nevertheless, the linkable ring signature will slowdown DPDP for increasing cost by the number of participants, and hence hinder piratical use of online collaborative systems. In this work, we propose TA-DPDP, a Dynamic Provable Data Possession for online collaborative systems with Tractable Anonymous, to resolve the aforementioned challenges. Our key insight is adapting linkable ring signature to DPDP with a new dynamic data structure. Such that, participants can audit ownership on their dynamic data under conditional privacy with optimized computational and storage overhead. Security analysis and evaluations justify security and practicality of our proposal.