Hydraulic　fracturing　is　a　key　technical　means　for　stimulating　tight　and　low　permeability　reservoirs　to　improve　the　production,　which　is　widely　employed　in　the　development　of　unconventional　energy　resources,　including　shale　gas,　shale　oil,　gas　hydrate,　and　dry　hot　rock.　Although　significant　progress　has　been　made　in　the　simulation　of　fracturing　a　single　well　using　two-dimensional　Particle　Flow　Code　(PFC2D),　the　understanding　of　the　multi-well　hydraulic　fracturing　characteristics　is　still　limited.　Exploring　the　mechanisms　of　fluid-driven　fracture　initiation,　propagation　and　interaction　under　multi-well　fracturing　conditions　is　of　great　theoretical　significance　for　creating　complex　fracture　networks　in　the　reservoir.　In　this　study,　a　series　of　two-well　fracturing　simulations　by　a　modified　fluid-mechanical　coupling　algorithm　were　conducted　to　systematically　investigate　the　effects　of　injection　sequence　and　well　spacing　on　breakdown　pressure,　fracture　propagation　and　stress　shadow.　The　results　show　that　both　injection　sequence　and　well　spacing　make　little　difference　on　breakdown　pressure　but　have　huge　impacts　on　fracture　propagation　pressure.　Especially　under　hydrostatic　pressure　conditions,　simultaneous　injection　and　small　well　spacing　increase　the　pore　pressure　between　two　injection　wells　and　reduce　the　effective　stress　of　rock　to　achieve　lower　fracture　propagation　pressure.　The　injection　sequence　can　change　the　propagation　direction　of　hydraulic　fractures.　When　the　in-situ　stress　is　hydrostatic　pressure,　simultaneous　injection　compels　the　fractures　to　deflect　and　tend　to　propagate　horizontally,　which　promotes　the　formation　of　complex　fracture　networks　between　two　injection　wells.　When　the　maximum　in-situ　stress　is　in　the　horizontal　direction,　asynchronous　injection　is　more　conducive　to　the　parallel　propagation　of　multiple　hydraulic　fractures.　Nevertheless,　excessively　small　or　large　well　spacing　reduces　the　number　of　fracture　branches　in　fracture　networks.　In　addition,　the　stress　shadow　effect　is　found　to　be　sensitive　to　both　injection　sequence　and　well　spacing.