Abstract: With the rapid development of storage technology, continuous data protection (CDP) has become an important data protection and recovery method for modern data storage systems now. According to the merits and shortcomings of existing CDP mechanism, an improved mechanism based on TRAP-4 (timely recovery to any point-in-time) is provided. It reserves the basic data logging method of TRAP-4 first, and then inserts a few snapshot data into the recovery chain by a certain interval values d. This mechanism can not only avoid the latent recover chain crash problem, but also can shorten the data recovery time greatly. A quantitative mathematical model is used to analyze its performance and calculate an optimal d value for ST-CDP. This prototype system of block level ST-CDP mechanism has been implemented in a Linux block level device (MD RAID 5 device for Linux kernel). Contrastive experiments among three different CDP mechanisms are presented. The performance test results show that ST-CDP not only have lower storage space overhead and less infection to the storage system than those of the traditional snapshot mechanisms, but also have higher recovery efficiency and reliability than TRAP-4. It is affirmed that ST-CDP is an efficient continuous data protection mechanism with very low recovery cost.