To　investigate　the　effects　of　ignition　position　on　the　explosion　of　non-uniform　methane-air　mixtures,　experiments　were　carried　out　in　a　closed　pipe　of　1　m　length　and　0.3m　x　0.3　m　cross-section.　Methane　is　uniformly　charged　at　the　top　of　the　pipe　and　then　diffused　freely,　creating　a　concentration　gradient.　The　concentration　gradient　of　the　methane-air　mixture　depends　on　the　diffusion　time.　The　effects　of　the　three　ignition　positions　-　top　(IP1),　center　(IP2)　and　bottom　(IP3)　-　on　the　flame　propagation　at　different　ignition　delay　time　(tig)　were　investigated.　The　ignition　position　and　tig　are　the　key　factors　influencing　the　success　of　ignition.　For　IP2　and　IP3,　the　flame　propagation　velocity　increases　with　the　increase　of　tig,　but　the　flame　propagation　velocity　at　IP1　does　not　change　significantly　with　an　increase　in　tig.　When　tig　＜=　25min,　the　temperature　(Tmax)　and　maximum　overpressure　(Pmax)　in　the　pipe　at　IP1　are　significantly　higher　than　those　at　IP2　and　IP3.　When　the　methane-air　mixtures　are　nearly　uniform,　the　Tmax　and　Pmax　at　different　ignition　locations　are　almost　identical.　The　maximum　pressure　rise　rate,　(dP/dt)max,　was　affected　by　the　flame　pipe　collision　and　different　flame　shapes　caused　by　the　ignition　position.