Abstract: Based on eight year long data from the Jinan Doppler Weather Radar, first of all, the concept for the back-development thunderstorms and rules for their identification are given. Secondly, the 75 back-development thunderstorm cases have been selected by examining the Jinan Doppler Weather Radar data from 2005 to 2012, statistical analysis of the back-development thunderstorms has been conducted over the midwestern area of Shandong Province, and then three major conceptual models of the back-development thunderstorm are proposed. Finally, detailed analysis of the evolution modes and physical mechanism for the back-development thunderstorm are conducted by investigating several typical cases. Some clues on the conditions for the initiation, maintenance and development of the back-development thunderstorms in the midwestern area of Shandong Province are revealed and discussed. The results show that: (1) During the back-development events, the shapes of main echoes are always band-like, their lifespans are between 1 to 5 hour, the maximum reflectivity is over 50 dBz, and there are three types of main echo moving paths including northwest, southwest and local generation. (2) The initiation time of the new echoes are mostly at 16:00-17:00 BT, and their initial positions concentrate on the northwestern and central areas of Shandong Province, their intensity goes up to 40 dBz within 30 minutes, lifespan is greater than 1 hour, and 74.7% of the new echoes connect with the main echoes. (3) The major disastrous weather produced by the back-development thunderstorm are hail and wind gust, seldom accompanied by severe rain. (4) There are three types of original source regions for the new echoes: moving with the main echo, extending along one direction, and located between two groups of thunderstorms. In the cases of several groups of thunderstorms present, the original source regions of new echoes would lie between two thunderstorm clusters, so that the two groups of thunderstorms tend to merge with each other. (5) When the propagation direction of main echoes intersects its long axis, the direction of that axis will turn, and the intensity in the part of main echoes located further from the new echo will turn weaker; when the propagation direction of main echoes is parallel with its long axis, the new echoes would develop along the extending part of the main echo long axis, leading then the main echoes to strengthening. And, (6) the synoptic-scale weather system provides conditional unstable atmosphere and abundant water vapor, while the boundary layer convergence lines and gust front are the main lifting mechanisms for initiating the new echoes. The suitable low level (0-3 km) vertical wind shear is conductive to the continuous generation and strengthening for the new thunderstorms. The original source regions of the new echoes would stagnate in the same place due to the block of terrain. The gust front in the leading edge of the cold pool moves downstream along the terrain by the steering of lower-level wind, and then the original source regions of new echoes would move with the gust front.