The invention provides a production apparatus and usage method of diesel vehicle exhaust treatment fluid. The apparatus comprises the following components: a bunker of high purity urea, a metering tank, an ultrapure water apparatus, a preparation kettle, a stirring and heating device, a buffer tank, an on-line quality analyzer, a membrane filtration apparatus, a product pot, a product pump, and connecting pipelines. The treatment fluid product is obtained by the following processes: metering, preparation, refining, etc. The apparatus is a set of integrated system which can be arranged in a gas station, and has the advantages of few land occupation, low investment, and flexible production; range limitation of production and sale of the diesel vehicle exhaust treatment fluid is solved, the product can be produced when the product is needed, so that the costs of production, transport and storage are reduced.