In order to study the anti-explosion stability of a long-span underground chamber under the influence of multiple factors,simulation using FLAC3D,based on model tests,was conducted by changing the parameters of explosion strength,explosion source location and chamber span,so that to obtain the variation laws of stress,displacement and plastic zone of the surrounding rock and lining structure of the chamber under different conditions.The research results show that the stress wave propagates in a spherical form from the explosion center.In the process of propagation,the strength of the stress wave rapidly attenuates,and the reflection occurs when the wave spreads to the earth's surface and the free surface of the chamber.The reflected tensile wave makes the surrounding rock damaged,producing the phenomenon of "spalling",and splayed cracks appear on both sides of the chamber.After the explosion intensity increases,the stress values of the measuring points and the deformation of the vault increase.The tensile area and plastic zone above the chamber also become larger,and even join together,which might make the chamber collapse.With the increase of the chamber span,the stress value of each measuring point changes little,while the deformation of the vault increases significantly,which results in a worse anti-explosion performance.Under the same explosion intensity,the damage effect of top explosion is the most serious.The more the explosion source deviates from the chamber,the smaller the stress values of measuring points,deformation and plastic zone of chamber are.As a practice,increasing the buried depth of the chamber and making some surface camouflage can reduce the explosion damage effect,while increasing the strength of lining structure and anchoring the arch foot and the vault can enhance the stability of the chamber.