TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: A micro-bypass is arranged on the outlet pipe of the reacting object of the microchannel heat exchanger. The pH detecting point (5) is mounted on the micro-bypass and is provided with a pH detector. The flow regulating element is a metering pump (2) and/or a pipe flow regulating valve. The metering pump and/or the pipe flow regulating valve are mounted on the pipes between two entrances of the storage container of the acid and the ammonia and the microchannel reactor. The flow regulating element comprises a pipe pressure indicating gauge, which is mounted on the pipes between two entrances of the storage container of the acid and the ammonia and the microchannel reactor. The microchannel reactor is composed of at least two entrance passages and at least one reacting passage connected with the entrance passages, respectively. The entrance passages are connected with two entrances of the raw materials. The reacting passage is connected with the exit of the product. The microchannel heat exchanger is composed of at least one cooling material passage and at least one coolant passage. The entrances and the exits are mounted on two ends of the cooling material passage and the coolant passage. A feeding distribution passage and a reacting passage are mounted between the entrance passage of the microchannel reactor and the reacting passage. The two feeding distribution passages are connected with the reacting passage by the holes. The microchannel reactor and the microchannel heat exchanger are assembled independently or integrated.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The acid is the phosphoric acid or the aqueous solution of sulfuric acid, hydrogen nitrate or oxalic acid. Preferred Method: The phosphoric acid and the aqueous ammonia water are used as the raw materials. The pH value of the product is controlled at 4.5-5.0 by the flow regulating element to generate the ammonium dihydrogen phosphate solution.