The invention relates to a plant growth bag device and protecting structure for slope ecological remediation and a construction method. The plant growth bag device comprises a plant growth bag, wood pulp paper, a seed layer, a coconut fiber net and a bag sewing thread or a self-locking type opening binding ribbon, and the growth planting bag is made of flax materials. The construction method includes: compacting and flattening a slope; loading planting soil into the plant growth bag devices; laying the plant growth bag devices on the slope; drilling the slope bottom foundation and the slope top protecting shoulder, and embedding expansion bolts with hooks into the holes; laying a steel wire mesh on the outer surfaces of the plant growth bag devices, and tightening and fixing the steel wiremesh to the slope; using anchor rods to anchor the plant growth bag devices to the slope. The plant growth bag device is high in stability on the slope and large in meshes, so that the germination and growth of monocotyledon and dicotyledon herbaceous plants are benefited; the materials and size of the flax plant growth bag are improved, and the single-cavity or double-cavity flax plant growth bag is used; the construction method of the protecting structure based on the plant growth bag device is improved, manual construction efficiency is increased, and cost is saved.