The utility model discloses an automatic drainage facility of gasholder for resolving the problems of prior artificial drainage facility of gasholder as long time consumption, affected production or product quality and waste of compression gas. The drainage facility comprises a drain pipe connected with the bottom of the gasholder, a drainage electromagnetic valve at the middle of the drain pipe and a timer connected with the control line of the drain electromagnetic valve. According to the demand on the drainage time of gasholder, the on time and off time of the timing switch can be set, the power line of timer is connected with a power supply, and the utility model can work, the on and off of the drainage of gasholder can be automatically controlled by the timing switch. The utility model has simple structure and the ability for resolving the defects of artificial drainage.