The invention provides a process unit capable of improving operation flexibility of a boiling flow heat transfer experiment and an implementation method thereof. The process unit comprises a low-temperature working medium circulation loop and a high-temperature conduction oil circulation loop, wherein a low-lift booster pump of the low-temperature working medium circulation loop is provided with two outlet pipelines; one outlet pipeline serves as a reflux bypass connected with a hot-side inlet of a cooler, and a hot-side outlet of the cooler is connected with a reflux connecting pipe positioned at the lower end of a barrel body of a vapor-liquid separation tank; the other outlet pipeline is connected with a cold-side inlet of a preheater, and a cold-side outlet of the preheater is connected with a cold-side inlet of a test section; a thermal oil furnace of the high-temperature circulation loop is provided with two outlet pipelines, one hot oil pipeline is connected with the hot-side inlet of the preheater, and the other hot oil pipeline is connected with the hot-side inlet of the test section; the hot-side outlets of the preheater and the test section are connected with an inlet pipeline of the thermal oil furnace. The process unit is high in pressure and temperature operation flexibility; during a low-temperature test, the pressure of a working medium can be up to 0.3-0.4MPa, and the temperature can be up to 30-300 DEG C; the process unit can be directly used in overall boiling and evaporation flow heat transfer experiments and performance tests for tubular and plate-type heat exchangers.