Using　mental　wires　to　generate　electric　arc　is　one　of　common　means.　The　wire　will　be　accompanied　by　shock　waves　at　the　moment　of　electrical　explosion;　In　addition,　the　arc　thermal　effect　will　also　lead　to　the　rise　of　pressure　inside　the　closed　container.　In　this　paper,　two　physical　processes　of　wire　electric　explosion　and　arc　thermal　effect　are　introduced　firstly.　Taking　the　pressure　wave　in　transformer　oil　as　an　example,　the　influence　of　the　two　physical　processes　on　the　pressure　characteristics　of　the　container　filled　with　liquid　is　analyzed.　In　order　to　further　study　the　pressure　characteristics　of　arc　of　the　container　filled　with　air,　an　short-circuit　test　platform　at　50　HZ　was　built.　Three　groups　of　short-circuit　tests　were　carried　out　by　controlling　different　current　peaks,　and　the　arc　burning　time　was　50ms.　The　results　show　that　the　pressure　increases　slowly　with　time,　and　the　higher　the　current　peak　is,　the　greater　the　pressure　increment　is.　With　the　increase　of　current,　there　is　no　shock　wave,　and　the　process　of　pressure　rise　corresponds　to　the　arc　burning　time,　so　it　is　determined　that　the　main　reason　of　pressure　rise　is　the　thermal　effect　of　arc.　The　research　content　of　this　paper　clarifies　the　physical　process　for　the　subsequent　pressure　rise　calculation　of　short-circuit　arc　of　the　cable　intermediate　joint　in　the　explosion-proof　box.