The embodiment of the invention discloses a railway cantilever construction continuous beam section elevation early warning method and a railway cantilever construction continuous beam section elevation early warning device, which can achieve the construction beam section elevation data over-limit real-time early warning of a railway concrete cantilever construction continuous beam bridge with a single-hole span of less than 100 meters. The method comprises the following steps: for each T structure of a railway cantilever construction continuous beam bridge, a top surface elevation value and atop surface elevation of the front end of a No.0 block of a cantilever beam section which has been constructed on the T structure are acquired; a corrected design elevation values of the front n-1 cantilever beam sections of the T structure after construction is calculated; according to the corrected design elevation values and of the front n-1 cantilever beam sections which have been constructedand the top surface elevation values of the front n-1 cantilever beam sections which have been constructed, the elevation deviation values of the front n-1 cantilever beam sections which have been constructed are calculated, and alarming is carried out when judging that any one of elevation deviation values of the elevation deviation values of the n-1 cantilever beam sections which have been constructed before being known is larger than a first alarming limit value.