The invention provides an alarm method and system based on model trend prediction. The alarm method comprises that a corresponding model is called from preset models according to relation between historical reference points and historical output points; the historical reference points and the historical output points are substituted into the model to calculate a model parameter; an evaluation value is calculated according to the model, the model parameter and the real-time historical reference point; the maximal absolution value of the difference between the evaluation value and the historicaloutput point is set as an alarm threshold; whether the difference between the real-time output point and the evaluation value is greater than the alarm threshold is determined; and if YES, an alarm signal is output. Thus, hidden safety hazards in the production process can be exposed in advance, and the production process is much safer and more economical.