The invention relates to normal-temperature-modified asphalt for a high-strength cold-laid asphalt mixture and a preparation method of normal-temperature-modified asphalt. The normal-temperature-modified asphalt for the high-strength cold-laid asphalt mixture comprises the following components in parts by weight: 58-64 parts of petroleum asphalt, 21-30 parts of a reactive diluent, 11-14 parts of a diluents, 0.01-1 part of a flame retardant and 0.01-1 part of a modifier. The normal-temperature-modified asphalt is small in viscosity at normal temperature and has good construction workability; the softening point of the normal-temperature-modified asphalt is higher than that of ordinary petroleum asphalt and the normal-temperature-modified asphalt has the advantages of large elastic recovery rate, short surface drying time, high curing-molding rate and strong coating force with an aggregate. The cold-laid asphalt mixture prepared from the normal-temperature-modified asphalt has the advantages of high early strength forming speed after paving, high molding strength and short open transportation time compared to the conventional cold-mixing asphalt mixture and meanwhile, the high temperature performance, water stability and the low-temperature performance can reach the technical requirements of the hot-mixing asphalt mixture and the preparation method is simple, economic, environmentally friendly and energy-saving.