The invention discloses a reinforced grounding current diffusion device of a power transmission line tower. The reinforced grounding current diffusion device mainly comprises needle grounding electrodes, a hollow column and a water injection pipe. The reinforced grounding current diffusion device has the advantages of simple structure, convenience in construction, low engineering cost, good current diffusion characteristic, low grounding resistance, corrosion resistance, zero environmental pollution and the like, can be widely applied to reducing grounding resistance, and is particularly applicable to arid regions, rocky regions, regions with high soil resistivity and regions with violent thunderstorm activities.