The invention is mainly applied to the technical field of diesel engine cylinder covers and particularly relates to a sand mixing technology for a water jacket core in a diesel engine cylinder cover casting blank. The sand mixing technology is characterized by comprising the following steps that firstly, 45 parts to 55 parts of ceramsite, 20 parts to 30 parts of chromite sand and 20 parts to 30 parts of quartz sand are weighed and mixed, and the above sand is evenly mixed; secondly, furan resin accounting for 1% to 3% of the mass of the above mixed sand is weighed, and para-toluenesulfonic acid accounting for 75% to 85% of the mass of the furan resin is weighed; thirdly, the weighed para-toluenesulfonic acid is poured into a molding sand mixing stirring machine to be stirred; and fourthly,the weighed furan resin is poured into the molding sand mixing stirring machine to be stirred, after the sand, the resin and the acid are evenly mixed, and the mixture is received through a sand hopper and is used for make preparation to forge the core. By means of the improvement on the sand mixing technology, the cleaning effect of a large water jacket cavity and a small water jacket cavity ofa cylinder cover is good, and the problem of sand sticking of the large water jacket cavity and the small water jacket cavity is solved. The problem that sand is wrapped in iron of the interior is completely solved.