Abstract: On the condition of a high Pulse Repetition Frequency (PRF) mode, radars may suffer from range ambiguity, which poses a significant challenge to detecting and tracking weak targets. To address this problem, a novel approach, which can handle ambiguous data of weak targets, is proposed within the Track Before Detect (TBD) framework. The main idea is that, without the pre-detection and ambiguity resolution step at each time step, the problem of range ambiguity resolution and target detection are transformed into the decision of the target true track. At first, the space-time relative information can be achieved by a multiple hypothesis ranging procedure, in which all the ambiguous measurements are handled via a batch procedure. Next, based on the relativity in time and PRF domains, the track is detected with a TBD method while the ambiguous data is unfolded. Different to classic methods, the new approach transforms the problem of range ambiguity resolution into the decision of the real track for targets, which provides a new way to such problem, avoiding the loss tracking of the weak target with lower Signal Noise Ratio (SNR). An application example is given to analyze and compare the performance between the proposed approach and the existing approach. The simulation results illustrate the effectiveness of this approach.