The invention discloses a retardation type low-alkalinity composite cementing material and a preparation method thereof. The retardation type low-alkalinity composite cementing material comprises a composite retarder solution and solid powder, wherein the mass ratio of the composite retarder solution to the solid powder is (0.37-0.43):1; the solid powder is prepared from, by mass, 30-50% of cement, 10-30% of slag, 5-20% of zeolite, 5-20% of metakaolin and 0-3% of an additive; the composite retarder solution is composed of monocalcium phosphate, sodium borate, boracic acid and a naphthalene water reducer; the cement comprises low-alkalinity sulphate aluminum cement and composite sulphate aluminum cement; the slag is S105-grade granulated blast-furnace slag, and the specific surface area ofthe slag is 460-500 m<2> kg<-1>. The setting time of the retardation type low-alkalinity composite cementing material can be adjusted from 3 hours to 8 hours, the pH value is lower than 11.5, the strength of the material at 28th day reaches 30 MPa or above, the problem about quick setting caused by low-alkalinity cement is effectively solved, and the technology is simple and convenient to use.