Disclosed is a mixed reactor and a method for preparing electrothermal film precursor solution based on the mixed reactor. The mixed reactor includes a reaction kettle body, a reflux condensation mechanism, and a multifunctional stirring mechanism. The reflux condensation mechanism includes a condensate tank, a condensing coil is wound around inside of the condensate tank, two ends of the condensing coil are horizontally arranged, and hermetically and rotatably installed on both sides of the condensate tank, the condensing coil is driven by a coil driving motor; the multifunctional stirring mechanism includes a stirring shaft and a plurality of stirring blades driven by the stirring shaft. The bottom of the stirring shaft is fixedly sleeved with an isolation sleeve. Buffer rubber gaskets are hermetically connected between the mounting parts and the installation holes. It can effectively improve the quality of products and the quality controllability during the product preparation process.