The invention discloses a deep mine loose coal seam roadway surrounding rock reinforcing method. The method includes: in a deep mine tunneling coal seam roadway, according to coal seam occurrence states and roadway cross section conditions, performing advance coal exploring and jet grouting pile size setting, and carrying out horizontal jet grouting at roadway cross section contour drill holes andadding reinforcing steel bars to form an advance roof jet grouting arch structure; performing jet grouting of anchor rods between U-shaped sheds arranged at intervals between two side portions to form a side horizontal jet grouting anchor pile group. The deep mine loose coal seam roadway surrounding rock reinforcing method takes full consideration of complexity of deep under-coal mine rock conditions, the roadway roof is reinforced by high-pressure jet grouting advance reinforcement to form the advance roof jet grouting arch structure high in bearing capacity, and accordingly working face collapse and roof caving in a tunneling process can be prevented, and safety in tunneling is guaranteed; the U-shaped sheds in the roadway behind a heading face cooperate with the side horizontal jet grouting anchor pile group to realize supporting, high supporting resistance is realized, intrinsic bearing capacity of roadway surrounding rock is given into full play, all-directional time-segmented roadway surrounding rock control is realized, and a stable surrounding rock bearing structure can be formed after tunneling.