The invention discloses a drilling and piling construction method for highway guardrails. In the method, with a first hole as a datum hole, a walking mechanism of a drilling machine walks along a redline for planning, the walking spacing is designed in advance based on the infrared ranging principle, the traveling distance of the walking mechanism is automatically detected and controlled according to the set hole spacing, and then drilling machine operators put down a drilling rod directly to complete a series of drilling and piling. Equally-spaced drilling and piling are automatically realized, it is avoided that the hole spacing needs to be manually measured in construction, and the construction efficiency is greatly improved; construction steps are strictly controlled, constructors encircle the construction site with yellow cordons and insert warning boards to warn passersby against getting close to the construction area, the constructors need to arrange protective fences around holes to reduce potential safety hazards of the construction site, and signboards with serial number marks are inserted near the holes so that the constructors can count conveniently. The method is especially suitable for drilling and piling construction of guardrails on highways.