The present invention is generated in a as, more particularly, but form a splashboard unit in the interior of the water tank, by forming an array of a plurality of splashboard crosswise, in case of an external shock, such as from an earthquake, the water tank on the SMC water tank severe and thereby sloshing effectively disperse the impact on, to prevent the occurrence of residues due to the damage or portion of the water tank compromised such as to minimize the impact transmitted to this side wall portion and a ceiling portion of the SMC water tank in accordance with, also, splashboard I in forming a unit, by making the respective rooms bolting, while applying the same specifications and the bottom panel of dashboard assembly structure and support the reinforcing structure using the steel bar with the side wall of the splashboard and the water tank, that result from the improvement of the mounting structure shock-proof by sloshing, etc. to lead to an increase in the durability of SMC water tank to be improved ensuring a castle and structural stability It relates to a fire protection water tank, and SMC splashboard unit installation method with a dashboard unit.