Modified emulsified asphalt relates to the modified emulsified asphalt product obtained by modifying petroleum asphalt by emulsifier. The modified emulsified asphalt consists of the following components with the weight percentages of 55 percent to 56 percent of the asphalt, 1.0 percent to 4.0 percent of petroleum acid quaternary ammonium salt cationic emulsifier, 1.5 percent to 5.0 percent of one kind or a mixture of the two kinds of the products of cationic styrene-butadiene rubber latex or cationic styrene-butadiene-styrene ternary block copolymer latex and 32 percent to 42 percent of water. The quality of the emulsified asphalt product completely meets the requirement of related national standard; the emulsified asphalt product has good adhesiveness with stone and good storage stability; the product adopts the byproduct of the petroleum asphalt produced during the course of processing naphthene base crude oil as raw material to prepare quaternary ammonium salt emulsifier, so the product has better compatibility with base asphalt and has better emulsification effect, very stable product performance and better low-temperature performance.