The invention discloses a comprehensive utilization method of high titanium slag in the slag treatment technology. The method comprises the following steps: firstly, carrying out acid leaching by using diluted hydrochloric acid; then, carrying out acidolysis by using dilute sulphuric acid, wherein the leaching rate is improved; using a black titaniferous liquid after acidolysis to prepare titanium dioxide; settling Fe(OH)3, Al(OH)3, Mg(OH)2 and Ca(OH)2 from a primary filtrate obtained by acid leaching and recovering sodium chloride; and using Si, Mg and Ca in slag to prepare an Si-Ca-P-Mg composite fertilizer. The method disclosed by the invention is extremely low in acid consumption of acid which is recycled, various effective components of high titanium slag can be comprehensively utilized, and factors in many aspects such as environment friendliness, technology and economical benefit are taken into consideration. The slag is low in cost, and titanium, ferrum, aluminum, magnesium, calcium, silicon, sodium chloride and the like can be comprehensively recovered, so that the economic benefit is remarkable, the long-term pendent problem on utilization of high titanium slag is solved, the land for slag is saved, the environmental pollution is reduced, wastes are turned into wealth, and the high titanium slag has a good social benefit.