The invention relates to a room environmental cleaner, and in particular relates to a room environmental cleaner which is safe, nontoxic and environmentally-friendly and has the effects of resisting bacteria, preventing corrosion and purifying air, and a preparation method thereof. The room environmental cleaner disclosed by the invention comprises the components including a living ionic surface active agent, natural mineral salt, superfine molecular diatomite, sodium diacetate, lemongrass oil and organic lemon tea tree hydrosol and is prepared from the following components in parts by weight: 10-20 parts of the ionic surface active agent, 1-5 parts of the natural mineral salt, 5-10 parts of the superfine molecular diatomite, 1-3 parts of the sodium diacetate, 0.5-1 part of the lemongrass oil, 5-10 parts of the organic lemon tea tree hydrosol, and the balance of de-ionized water. The invention further relates to a preparation method of the room environmental cleaner. The room environmental cleaner disclosed by the invention is safe, nontoxic and environment-friendly and has the effects of resisting bacteria, preventing corrosion and purifying air, so that the room environmental cleaner is widely applied to room cleaning in hotels, homes and the like.