The invention discloses an online laser process device for railway rail surface tenacious treatment, which includes a laser processing vehicle and a power mobile machinery shop. The laser processing vehicle includes a motion actuator, a laser processing head, a control system and/or automatic powder feeder equipped on a moving trolley; the power mobile machinery shop includes a dynamo, a freezer, an air compressor, a refrigerated air dryer and a laser high voltage source equipped on a lorry. The laser processing head is equipped on the motion actuator; the laser processing head is connected to the laser directly or by a light guiding system. The invention can finish laser surface quenching, fused quenching, alloying and cladding on various rails, including rail, bend, guard rail, turnout, etc., without dismantling rail and affecting the normal operation of a train, the processed rail has greatly lengthened its wearability, and has characteristics of easy dismantling, high processing precision and easy operating.