Methods, devices, and systems for data monitoring are provided. In one aspect, a method of data monitoring, applicable to a magnetic resonance system, includes: obtaining radio frequency (RF) waveform information which is to be sent to an RF transmitting coil of the magnetic resonance system; extracting target waveform information within a current sliding window from the RF waveform information, with a current time point being located within the current sliding window; obtaining, based on the target waveform information, target magnetic flux densities corresponding to the current sliding window; and determining a current real-time specific absorption rate (SAR) based on the target magnetic flux densities.