The invention relates to an earthquake magnitude rapid estimation method based on initial P waves of a single station. According to the method, time-domain and frequency-domain analysis is performed on detected initial 1.5-second P-wave signals, so that an earthquake magnitude estimation formula which integrates various parameters and is composed of time-domain amplitude parameters and frequency-domain period parameters; and coefficient regression is performed on the parameters in the earthquake magnitude estimation formula through using the strong vibration records of Japan and a differentialevolution algorithm, so that a final earthquake magnitude estimation formula is provided. With the method of the invention adopted, an earthquake magnitude can be estimated with only the initial 1.5-second P-wave signals of the single station required. The method of the invention has the advantages of high accuracy, timeliness and usability, and is suitable for earthquake monitoring and earthquake early warning.