The utility model discloses a time delay estimation circuit based on zero -crossing detection, including an input circuit, the 2nd input circuit, a zero cross detection circuit, the 2nd zero cross detection circuit, time calculation circuit, a zero cross detection circuit and an input circuit establish ties, and the 2nd zero cross detection circuit and the 2nd input circuit establish ties, parallelly connected back of a zero cross detection circuit and the 2nd zero cross detection circuit and time calculation input circuit 2. An input circuit combines a zero cross detection circuit to realize that an input circuit incoming signal's zero -crossing time detects t1, the 2nd input circuit combines the 2nd zero cross detection circuit to realize that the 2nd input circuit incoming signal's zero -crossing time detects t2, the time calculation circuit carries out time calculation to zero -crossing time t1 and t2, draws two way signal delays and calculates triangle t as a result. The delay operation that the computing power of specially adapted system is limited, the consumption requires low regular signal.