The invention discloses a constant-temperature incubator for cell culture and relates to the technical field of bioengineering devices. The constant-temperature incubator comprises an incubator body, a placing table is arranged in the incubator body, an air inlet is formed in the incubator body, a rotating shaft is arranged in the incubator body, a turntable is fixedly connected to the rotating shaft, the rotating shaft is rotatably connected with a breather pipe through a linear bearing, an air outlet is formed in the incubator body, and a linkage mechanism is arranged in the incubator body. By arranging a piston, a conductive rod and a ventilating fan, an air pressure difference generated when gas components in the constant-temperature incubator change pushes the piston to drive the ventilating fan to work, so that gas exchange occurs inside and outside the constant-temperature incubator to maintain an oxygen concentration in the incubator, cell culture is always in air with a proper oxygen concentration, the ventilating fan can be automatically turned off after gas exchange is completed, and thus energy consumption is reduced.