The present invention provides a method for early warning of an abnormality sign of a device, which includes device importance and warning validity determination, and a system therefor. The method for early warning of the abnormality sign of the device comprises: a first step of determining by an early warning processing apparatus whether a device monitoring signal value exceeds a normal operation range by using a weight value on the basis of monitoring-parameter-specific importance data which has been previously analyzed by an operator; a second step of generating a warning by the early warning processing apparatus when the device monitoring signal value exceeds the normal operation range; and a third step of determining by a warning determination apparatus whether the generated warning is a valid warning, which is subject to a warning analysis and to be traced.