An atypical dynamic phenomenon of mines, including its action forms and definition, were put forward, based on the mining accident at the Furong Mining Group Company in Sichuan, P. R. China. The mechanism of the atypical dynamic phenomenon was revealed by analyzing rock stress distribution, calculating the first and cycle broken distance of each thick and hard roof, and analyzing the balance structure of broken rock based on the threedimensional finite element software. The first stratum of the bent, sunken, aged strip was influenced by the geological conformation and the coal mining activity. This created the first break of the key stratum and led to the atypical dynamic phenomenon. We show that the key factors affecting the phenomena are the roof and floor structures, surrounding rock, and initial stress and rock burst tendency of the key stratum.