The invention provides a microseismic monitoring first arrival picking method. The method comprises the steps: carrying out the linear decomposition of the first arrival trend of the microseismic data into a plurality of linear or approximately linear first arrival picking sections, and picking the peak first arrival, valley first arrival or jump point first arrival of each piece of microseismic data in each first arrival picking section. Compared with a manual picking method, the method greatly reduces the time, and improves the data processing efficiency.