The present invention provides a control method of a server, wherein the control method includes the steps of: periodically controlling a first register and a second register of a first node to have a first value and a second value, respectively; periodically controlling a third register and a fourth register of a second node to have a third value and a fourth value, respectively; controlling the first register and the fourth register to synchronize with each other, wherein the first value is different from the fourth value; controlling the second register and the third register to synchronize with each other, wherein the second value is different from the third value; and periodically checking if the third register has the third value and the fourth register has the fourth value to determine if the first node fails to work.