Abstract: Objective: To investigate what anorectal dynamic abnormality exits in elderly patients with chronic idiopathic constipation（CIC）. Methods: Study was performed in 59 elderly patients with CIC,36 elderly healthy subjects（EHS）,and 15 non-elderly healthy subjects. Anorectal pressure was measured with Medtronic PcPolygraf,which was a water perfuse catheter system. Results: 1.The anal resting pressure（RP）, maximal squeezing pressure（MSP） and the changes of anal pressure during defecation in elderly healthy subjects（EHS） were lower than those in non-elderly healthy subjects（NEHS,P ＜0.05）. The length of anal sphincter in EHS was shorter than that in NEHS（P ＜0.05）. The rectal lowest volume of sensory threshold（RLSTV） and the minimum relaxation volume of inducing anorectal inhibitory reflex were higher than those in NEHS（P ＜0.05）. 2.MSP and the changes of anal pressure during defecation in elderly patients （EP） with CIC were lower than those in EHS（P ＜0.05）. The RLSTV,the rectal threshold volume for desire to defecate and the rectal maximal volume of tolerance were higher than those in EHS （P ＜0.05）. And there were 28 （47.5%） of EP who had increasing anal pressure when defecation was stimulated. Conclusions: 1.There were some anorectal functional disturbances in EHS,such as the decreasing of anal resistance,increasing the volume of sensory threshold and the slowness of reflux motion. 2. CIC in elderly parients may be associated with lower sensitivity,higher tolerance and discoordination of annorectum during defecation.