The invention relates to the technical field of ladle heat insulation, and particularly relates to a casting molded ladle prefabricated heat insulating brick. The casting molded ladle prefabricated heat insulating brick adopts a raw material formula as follows in part by weight: 15 to 30 parts of first andalusite, 20 to 40 parts of second andalusite, 5 to 15 parts of third andalusite, 5 to 10 parts of high-purity lightweight material mullite, 5 to 20 parts of tabular corundum fine powder, 1 to 6 parts of activated aluminium oxide, 2 to 10 parts of calcined alumina, 3 to 10 parts of nano silicon dioxide aerogel particle powder, 6 to 20 parts of chopped alumina silicate fiber, 18 to 45 parts of binding agent, 0.08 to 0.2 part of dispersing agent and 0.05 to 0.5 part of coagulant. According to the invention, the formula of the ladle heat insulating brick is improved; the using region of the casting molded ladle prefabricated heat insulating brick is between a nano heat insulating plate and a safety permanent layer castable; after the nano heat insulating plate with a thickness of 5 to 7mm is adhered to the inner wall of a ladle wall steel shell, the prefabricated heat insulating brickdisclosed by the invention is adhered with fire clay, and then a die is fed to cast a safety permanent layer. Such mode improves a problem of excessive thickness of the heat insulating plate, also improves a problem of poor heat insulating effect caused by an excessively thin insulating plate, improves safety of use, the heat insulating effect and the service life of the ladle heat insulating layer.