The invention discloses a boiler early warning method and an early warning device. The early warning method comprises the following steps of acquiring shape data of a boiler drum; acquiring a thermalstress model of the boiler; acquiring a stress field model of the boiler; performing a finite element analysis on the thermal stress model and the stress field model to run a simulation model to obtain simulation parameters of the boiler; collecting operating parameters of the boiler every other fixed time; and comparing the acquired operating parameters of the boiler with the simulation parameters obtained by running the simulation model, and outputting an early warning signal. By means of the thermal stress model and the stress field model of the boiler, the finite element analysis method isutilized to obtain the simulation model which is closest to the normal work of the boiler, and the collected operating parameters of the boiler are compared with the simulation parameters obtained byrunning the simulation model; when the error of the operating parameters and the simulation parameters exceeds an error range, the early warning signal is output, so that the potential safety hazardof the boiler can be warned, and the fault risk of the boiler can be reduced.