An operation system for umbrellas includes a multiple-section shaft with a top cap connected to a top thereof and the top cap has a first extension which includes a flexible part formed thereto. A protrusion extends from a distal end of the flexible part. A runner is movably mounted to the shaft and the first extension. The runner has a second extension which has a positioning hole so as to receive the protrusion to stop the runner from moving downward. A hollow sleeve is movably mounted to the second extension and drives the runner to move along the shaft. The sleeve has a compressing member to compress the protrusion inward to disengage the protrusion from the positioning hole when folding the umbrella.