The invention discloses a composite automobile exhaust purifying agent and belongs to the technical field of purification of automobile exhaust. The composite automobile exhaust purifying agent comprises the following components in percentage by mass: 30-60% of butyric acid dioctyl phthalate, 10-20% of n-hexanol, 5-15% of cyanuric acid, 1-5% of sodium hydroxide, 1-5% of copper sulfate, 10-30% of Pt-Rh alloy and the balance of combustion improver, wherein the purity of the butyric acid dioctyl phthalate, the n-hexanol, the cyanuric acid, the copper sulfate and the sodium hydroxide is more than 99%, and the ratio of Pt to Rh in the Pt-Rh alloy is (1:1)-(5:1). The components of the composite automobile exhaust purifying agent are not in high price, and the composite automobile exhaust purifying agent is relatively easy to prepare, has the effects of lubricating and supporting combustion and has an obvious effect of absorbing the automobile exhaust.