A method for pre-assessing the temperature of tissues surrounding active implants under magnetic resonance (MR), applicable to a magnetic resonance imaging (MRI) system (20) which is used to generate a temperature-testing sequence, a test sequence and a sequence to be scanned, the method comprising: step S20: before executing the test sequence, use the temperature-testing sequence to perform temperature testing M times, wherein M≥1; step S30: executing the test sequence, and during the process of which, use the temperature-testing sequence to perform temperature testing N times, wherein N≥0; step S40: after executing the test sequence, use the temperature-testing sequence to perform temperature testing P times, wherein P≥1; and step S50: calculate a safety index on the basis of radio frequency energy correlation parameters of the test sequence as well as radio frequency energy correlation parameters of the sequence to be scanned; and compare the safety index to a threshold; if safe, perform scanning; otherwise, reject scanning.