The invention discloses a formula for treating arthritis and a preparation method of the formula, in the composition, a centella asiatica extract has the effects of clearing heat and promoting diuresis, detoxifying and eliminating swelling, a ficus hirta vahl extract has the effects of strengthening tendons and activating collaterals, and tonifying spleen, a pine needle extract has the effects ofdetoxifying and relieving itching, a beautiful millettia root extract has the effects of strengthening tendons and activating collaterals, a panax notoginseng extract has the effects of stopping bleeding, breaking blood and dissipating blood stasis, diminishing inflammation and relieving pain, and a scorpion extract has the effects of activating meridians and relieving pain, counteracting toxin and removing stasis. The centella asiatica extract, ficus hirta vahl extract, pine needle extract, beautiful millettia root extract, panax notoginseng extract and scorpion extract are prepared accordingto a specific ratio, and the components are irreplaceable. Through the synergistic effect with a baked ginger extract, the beautiful millettia root extract, a corydalis saxicola bunting extract, a atractylodes lancea extract, a mulberry twig extract, a lycopodium clavatum extract, a divaricate saposhnikovia root extract and a chili extract, the liquid spray prepared from the composition is remarkable in arthritis treatment effect, high in cure rate and free of toxic and side effects of hormones.