The invention discloses a packing fluid for branch well drilling, which comprises the following ingredients in parts by weight: 100 parts of water, 3-5 parts of micelle tackifier and 2-4 parts of fluid loss agent, wherein the micelle tackifier is a surfactant; the water is fresh water or sea water; and the fluid loss agent is one of modified starch and emulsified paraffin. By using the packing fluid, the oil well does not need to be subject to gel breakdown at the later stage of well completion, and the packing fluid can automatically finish gel breakdown when encountering formation oil during the setup of the oil well. Besides, the packing fluid causes less damage to the reservoir, realizes the maximum protection on the hydrocarbon reservoir and can increase the productivity of the oil well.