The present invention provides a preparation method of a fluorescent screen of a transmission electron microscope, which comprises the following steps: firstly, respectively carrying out the granularity selection on fluorescent powder and adhesion powder; drying the obtained powder; weighing and mixing the powder proportionally; then, using an ultrasonic dispersing method and a filtering method for uniformly dispersing the mixed powder into ethanol to obtain mixed suspension according to the proportion of the mixed powder and the ethanol; pouring the mixed suspension into a precipitation device (substrate glass provided with a conductive layer and an antireflection coating is placed in the precipitation device in advance); still standing the suspension until all powders are precipitated to the bottom; then, discharging the flow to slowly drip out the ethanol liquid; taking out a fluorescent screen pre-precipitation assembly and placing the fluorescent screen pre-precipitation assembly in a protective cover when the powder layer on a substrate is dried for forming the fluorescent screen pre-precipitation assembly with the fluorescent powder thickness between 10 and 50 mum; and simultaneously placing the fluorescent screen pre-precipitation assembly and the protective cover into a furnace to be sintered so that the fluorescent powder grains, and the fluorescent powder grains and the substrate can be glued when adhesion powders are fully melted for forming firm fluorescent screen sintering assemblies. The invention can overcome the defects of the traditional fluorescent screen preparation and processing, the quality of the precipitated fluorescent screen can be improved, the service life of the precipitated fluorescent screen can be prolonged, and the problem of difficult maintenance can be solved.