Abstract: A bispcetrum based method of time-delay estimation is used for the flowmeter in the oil well. The accuracy of the flowmeter in the oil well is determined by the accuracy of time-delay estimation. When we use the cross-correlation method, high accuracy could not be achieved in existence of correlated Gaussian noise. However, because the bispcetrum based method of time-delay estimation could theoretically eliminate Gaussian noise, we use the bispcetrum method as the substitution of the cross-correlation method. Both simulation and analysis of data acquired by the ultrasonic flowmeter prototype are implemented to reveal the differences between bispectrum based method and cross-correlation method.