A control method and a control system of tension in the process of rolling periodic variable-thickness strips belong to the technical field of rolling. The method comprises the following steps: dividing segments on the rolled pieces, setting front and back tension values in each zone, realizing tension open-loop control and tension closed-loop control based on maximum torque limit and adding a dynamic torque compensation link and a mechanical friction torque compensation link; controlling torques of an uncoiler and a coiling machine motor and setting speed. The system comprises a rolling mill; coiling machines are arranged at both sides of the rolling mill respectively; length-measuring rollers are arranged between the coiling machines and the rolling mill; thickness gauges are arranged at both sides of the rolling mill respectively; coil diameter gauges are arranged on the coiling machines; a rolling force sensor and a hydraulic cylinder are arranged on the rolling mill; tensiometers are arranged below the length-measuring rollers and pulse coders are arranged on the length-measuring rollers; the thickness gauge, the coil diameter gauge, the rolling force sensor, a displacement sensor of the hydraulic cylinder, the tensiometer and the pulse coder are respectively connected with a computer control system.