The invention discloses a parking lot real time early warning method under a present monitoring device, which is used for monitoring the vehicle parking condition, particularly the indoor parking lot, actively warning when abnormity happens and improving the reliability and safety of the parking lot. The parking lot real time early warning method comprises steps of fully utilizing the current monitoring equipment resource, considering the flashing characteristics of the automobile double flash lamps, using the grid clustering method in a color space model YCbCr to identify the flashing condition of the double flashing lamps of the parked automobile, performing Cr component clustering on the on the divided grid according to the changing condition of the Cr component, determining whether the double flashing lamps flash according to the cluster result and performing determination on the flashing condition of the double flashing lamps. The parking lot real time early warning method can realize the daily low-overhead and high efficiency independent operation and is low in complexity, high in accuracy, strong in implementation and high in flexibility.