The aim of this study is to analyze the correlation of two spatial resolution of CT image acquisition method（modulation transfer function method and line pair method） under low dose conditions,which to provide an objective basis for spatial resolution evaluation of CT quality control.This research scanned located mid-line CPT 528 and 486 module of Catphan 500 phantom by using GE Light Speed 16 CT under standard chest scanning conditions（120kV,200mA） and low dose conditions（80kV,100kV,120kV,and 140kV four gears; 10-60mA,10mA increased） separately,with CPT486 module measuring noise.Adjust the window wide and window level,observe distinguishable lines on the card under different scanning conditions（to illustrate the impact of subjectivity on the line pairs method,randomly selected parts of CPT528 scanned images were read by five testers and the results were statistically analyzed）.The point spread function（PSF） on the different locations were measured via the program,and then on two-dimensional Fourier transformation of PSF to get modulation transfer function（MTF）.Finally,we used SAS8.2 software statistical to analyze 10% MTF values and visual values in order to search the correlation between MTF method and line pairs method.The results show that when the MTF is 10% the corresponding spatial resolution and visual values obtained by lines pair method are consistent（t’=0.18,p=0.8556）.Under low-dose conditions,part of MTF curves are influenced by noise,leading to increase of MTF value.