The invention discloses a formula of a building indoor wall surface coating and a preparation method. The formula consists of water, titanium dioxide, a wax emulsion, sorbitan monostearate, white oil, spermaceti wax, propylene glycol, a styrene-acrylic emulsion, dipropylene glycol butyl ether, propylene glycol monomethyl ether, polyurethane resin, broad spectrum bactericides, bamboo charcoal factors, PVC (Polyvinyl Chloride) resin powder, nano calcium carbonate, talcum powder, xylene, acrylic resin, calcium carbonate, aluminum stearate, and butanol. Compared with the prior art, a finished product of the formula is an aqueous wall coating, is capable of adsorbing harmful substances of self and harmful substances in the air due to the carbon charcoal factors, has effects of good viscosity, peeling resistance, dampness resistance and sterilization due to multiple resin materials, is environmentally friendly and scientific, is beneficial to human body health, is free of odor, and has popularization and application values.