The invention provides a reinforced composite geotechnical cushion capable of preventing the capillary barrier effect and a manufacturing method thereof. The composite geotechnical cushion is formed by sandwiching a gravel and hemp thread layer, a hot-melt plastic wire layer and a reinforced grating layer. The reinforced composite geotechnical cushion is used in the side slope embankment filling anti-sliding reinforcement project and is particularly suitable for a side slope embankment filling project in a region with more rainwater in the south, the capillary barrier effect of infiltration rainwater at the reinforced layer can be remarkably reduced or eliminated, the infiltration speed of the rainwater can be increased, the seepage along the slope surface can be reduced, and the infiltration damage of soil mass can be avoided; and meanwhile, the composite geotechnical cushion can also improve the anti-sliding performance of the side slope soil mass and reduce the risk of landslide.