The invention discloses a deep foundation pit support construction monitoring early warning method. The method comprises the following steps: firstly, arrangement of foundation pit support monitoring; secondly, monitoring of foundation pit support; and thirdly, early warning; by means of the monitoring early warning method, fine changes of support structural inner force and changes of soil properties can be known in time, and the observation information can be fed back in time; preparation is made for dangerous cases possibly appearing and endangering the surrounding building, the deep foundation pit safety and the road safety in advance, and the repairing and reinforcing measures are taken in time.