Zero cross time detection method is very important in the phase measurement of powerfrequency AC signal. The detection uncertainties of most of the CMOS comparator based methods are around 200 µs, which cannot satisfy the high accuracy phase measurement. We proposed a new detecting method with higher accuracy by processing the sampled sequence of the under-test signal to estimate the relative frequency and phase sequentially. We implemented this method on a low-costSoPC (system on a

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... chip), and used oscillation multiplication technique to improve the detection uncertainty to 1µs. We designed a test bench and tested the implemented detector and the results illustrated the performance of this method.