The utility model relates to an automatic bag taking and packaging mechanism, which is characterized by comprising a left suction plate, a right suction plate, a sealing device and a sample bag box. The left suction plate and the right suction plate are arranged on a platform and are controlled by a vacuum generator, the sample bag box is arranged under the platform, one suction plate is controlled by a bag taking motor to rotate through a suction plate arm, and the other suction plate is controlled by a packaging cylinder to flex. The utility model operates as follows: the bag taking motor drives the right vacuum suction plate to take a bag in the sample plastic bag box and then to rotate into a horizontal position, the cylinder drives the left vacuum suction plate to absorb the other side of the bag so as to open the bag, and when samples are filled, the cylinder drives a heat sealing press block to press a heat sealing bar to package the bag. The utility model has simple structure, is convenient to use, and can realize fully automatic bag taking, opening and packaging. Moreover, the utility model is particular suitable for automatic packaging of cigarette samples during three-point testing of cigarette samples.