Abstract： Objective To study the hippocampal structure in the patients with depression in varying degrees of severity with the combination of the susceptibility weighted imaging (SWI) and morphological measurement.Methods Sixty patients (divided equally into mild,moderate and major group as the conditions of the severity of depression) and 20 healthy controls were scanned using the three dimensional fast low angle shot imaging sequence (3 D-FLASH) and SWI.Then the morphological images were manually segmented and delineated by three doctors.The hippocampal volumes were calculated and standardized.The maximum diameter,length and the branching numbers of the Inferior ventricular vein which were clear demonstrated in the SWI were measured.The changes in the venous system and morphology among the three different degrees of severity in depression and the healthy controls were contrastively analyzed by the one-way analysis of variance.Results Left and right hippocampal volumes: the mild group were 2246 ± 147,2271 ± 151; the moderate group were 2028 ± 65,2038 ± 57; the major group were 1965 ± 129,1962 ± 110; the healthy control were 2287 ± 160,2305 ± 171.There were statistically significant differences among the four groups (F =7.45,8.55,P ＜ 0.01).The hippocampal volumes of depressive patients were smaller than that of the healthy controls,with the biggest variability occurred in the major depressive patients (Dunnett-t =-7.04,-7.54,P ＜0.01) and the second in the moderate group (Dunnett-t =-6.73,-6.64,P ＜0.01).There were no statistical significant difference between the mild group and the control (Dunnett-t =-0.85,-0.67,P ＞0.05).The diameter,length and branch numbers of the lateral ventricle vein: the mild group were (0.94 ± 0.09) mm,(12.0 ± 1.07) mm and 3.67 ± 1.03 ; the moderate group were (0.81 ± 0.04) mm,(10.2 ± 1.25)mm and 2.00 ± 0.89 ; the major group were (0.70 ± 0.08) mm,(8.6 ± 1.40)mm and 1.83 ± 0.75 ; the healthy control were (1.15 ± 0.14) mm,(14.2 ± 0.90) mm and 3.33 ± 0.82.There were statistically significant differences among the four groups (F =17.07,25.20,6.65,P ＜ 0.05).The lateral ventricle vein's length,diameter reduced significantly in the mild group (Dunnett-t =-5.64,-7.04,P ＜0.01),but the branch numbers were increased,which was closed to statistical differences (Dunnett-t =1.85,P ＞ 0.05).As the progressive of the depression,the reduction in the length,diameter and branch numbers of the lateral ventricle vein showed more evident (the Dunnett-t of the moderate were-10.20,-11.50,-2.88,P ＜ 0.05 ; the Dunnett-t of the major were-11.70,-14.69,-5.76,P ＜ 0.01).Conclusion The combination of the SWI and morphological measurement helps to prompt the regularity of the changes in hippocampal structure in patients with different severity of depression.