The invention relates to a lower alloy steel laser-electric arc hybrid welding method in the technical field of metallurgy, machinery, ships, automobiles, pipelines, petrochemical industry, marine equipment, pressure vessels, war industry and the like. In order to solve the problems existing in a traditional welding method, on the basis of the effect law of laser-electric arc coupling characteristics and laser-electric arc hybrid welding parameters, the welding parameters and the groove sizes of all welding joints of multilayer welding are optimized with the orthogonal design test method, and the researched and developed lower alloy steel laser-electric arc hybrid welding method has the advantages of being small in heat input amount, large in fusion depth, small in deformation and high in welding speed, capable of reducing the area of the welding joints, the width of the heat affected zone and the exhaust amount of harmful gas and smoke and favorable for improving welding quality and welding efficiency, lowering production cost, improving the quality of products and relieving environmental pollution. The method includes the processing steps that welding grooves are machined, the optimized welding parameters are adopted for all the welding joints of the multilayer welding, and lower alloy steel laser-electric arc hybrid welding is performed.