Abstract: The new prospecting orebody in the northern area of Xishimen Iron Mine belongs to gently inclined，fractured and thick to medium thickness orebody with serious ground pressure，which is extremely difficult to mining.Pillarless sublevel caving mining method is adopted in the mine，problems such as poor operation of equipment，instability of stope structure and roadway failure seriously are existed during the mining process.In order to alleviate the mining problems caused by high stress and fragmentation，the mining technology is improved from the aspects of equipment selection，determination of stope structural parameters，roadway layout，mining sequence and support measures.On the premise of ensuring smooth operation of equipment，it is determined that the scraper should be increased from 1.5 m3 to 2 m3 and the roadway section size should be increased from 3 m×3 m to 3.2 m×3.1 m under the condition of weak and soft surrounding rock；the section height is 13 m and the route spacing is 12 m which are determined by considering the stability of roadway，orebody conditions，rock drilling capacity and the development of discharge body；based on the principle of adapting to the law of ground pressure activity，it is determined that the mining route is better laid out vertically and the mining sequence is better to withdraw from the boundary of the orebody to the upper wall；supporting requirements of the surrounding rock with large ground pressure and easy to fall in a short time after excavation are analyzed，and the supporting measures of advanced bolt and U-shaped steel arch are proposed；the minimum side hole angle is 50°，which is determined according to the flow parameters of bulk，and the caving step is adjusted to 1.6 m according to the outcropping position of waste rock at the ore outlet.The above parameters and support measures have been successfully applied in the mining process of high stress fractured orebody in the northern area of Xishimen Iron Mine，therefore，the applicability of mining such orebodies of sublevel caving mining method without bottom pillar is enhanced.

Key words: Sublevel caving mining method without bottom pillar, Gently inclined orebody, Broken orebody, High stress, Thick to medium thickness orebody, Stope structural parameter, Surrounding rock supporting