The invention relates to a method for conveniently and fast observing stem tip flower bud differentiation of tobacco plant, belonging to the technical field of developmental biology of plants. The method comprises the following steps: a. taking a sample with a blade at the position which is 5 centimetres downward from the stem tip; b. after sampling, immediately placing the stem tip in an ordinary injector for medical use, which has a volume of more than 15mL, pushing a pushing rod of the injector to the bottom, using a thumb to block the front part of a needle tube and forcefully pulling up the pushing rod to the top of the injector; retaining the position for 1-3min and repeating the process for 3-4 times; c. fixing the stem tip sample in a stationery liquid for 24h for testing with components having the following proportioning: 5.0mL of formaldehyde with a concentration of 38%, 5.0mL of acetic acid, 90.0mL of alcohol with a concentration of 75%; d. using a stereomicroscope to observe and take photos of the sample. The method has the advantages of low cost, simple and convenient operation, fast observation and acquisition of digitalized pictures with clear images, thus being of great guiding significance for experimental studies.