The invention relates to the field of near-line strain monitoring of high-temperature high-pressure metal components, in particular to a device and method for utilizing the white light speckle correlation technology to monitor the strain of the high-temperature components of a power plant in a non-contact and near-line mode. The device comprises a locating substrate (2), a strain sensor (3) and a fixed focus camera (4). According to the device and method, creep damage conditions of the high-temperature metal components, operated at high temperature for a long time, of the power plant can be accurately monitored, and the production accidents caused by failures and damage of the components due to high-temperature creep are avoided. In order to evaluate the service life of equipment, the creep strain of the high-temperature metal components of the power plant is monitored, creep strain accumulation measured values are utilized to conduct service life evaluation, so that the evaluation result is prevented from being too conservative, and the service life of the equipment is prolonged. Overhauling time of the equipment of the power plant can be determined according to the creep strain result, and the state of the equipment is used as the basis of overhauling, so that maintenance load and overhauling cost are reduced, and economy of the power plant is improved.