The hydropower condition monitoring alarm value ere studied in the paper, due to the change of operation conditions, the monitoring parameters of the unit had a huge impact, if the alarm value was too small, the hydropower alarm value cannot achieve full condition; if the alarm value is too big then it had no use in the good condition, In this article, A dynamic alarm curve model is proposed, take the head cover vertical vibration as an example, establish dynamic alarm curve model, GA-BP neural network model was established, the head cover vertical vibration is obtained by training and output dynamic curve of alarm.