A mechanism of controlling water outflow of shower is provided in the casing of shower. The water outlet of the mechanism is aligned with the water outlet of shower. The mechanism of controlling water outflow comprises inner sealing shell, outer sealing shell, and an intermediate cavity defined between the inner sealing shell and the outer sealing shell. A water outflow cavity is formed between outer sealing shell and water outflow disc. The intermediate cavity communicates with intake channel of shower. The mechanism of controlling water outlet also comprises separating sealing pad inside the intermediate cavity, with one side sticked to the water outflow disc of outer sealing shell and the other side sticked to valve elements. The intermediate cavity comprises the inner cavity and outer cavity. The inner cavity communicates with water outflow cavity through the first small hole and with outer cavity through a through-hole. The intake channel communicates with outer cavity. The small hole matches with a mobile sealing pad that connects the button kit that controls the sealing pad to separate or contact the small hole. This invention can realize different effects of water outflow, easy operation handle and longer service life.