Abstract: Deadtime corrections of three in-situ HPGe γ spectrometers were studied by experimental method of interference-method with strong γ source. The linear relationships between the percent deadtime and the correction coefficients were fitted by the least-square-method. The comparisons between the experimental results and the automatic correction values of full-energy-peak count rates were performed. The results show that the maximum deviation of the automatic correction values relatively to the experimental results is less than 4.4%. It indicates that in the deadtime range of 1.13%-52.95%, the automatic correction results of deadtime by these spectrometers themselves are exact and the deadtime correction techniques of modern γ spectrometers are efficacious, which can be used in the data analysis of γ spectra.