A closed algal culture barrel can control the irradiation wavelength, the frequency and the time of a light source in a tank body accurately, and further improve the growth rate of cultured algal. The closed algal culture barrel comprises a groove body, an upper cover and at least one light emitting device, wherein the groove body is used for accommodating a liquid medium for culturing algal; the groove body is made of a light-tight material and comprises at least one side wall, a bottom and an upper opening; the side wall is arranged in the longitudinal length direction of the groove body, and comprises an algal inlet end arranged on the side wall; the groove body has the height H in the longitudinal length direction; the bottom is connected with the side wall, and comprises a collection outlet end arranged on the bottom; the upper opening is formed above the groove body; the upper cover is used for covering the upper opening, and is made of a light-tight material; the light emitting device is arranged in the groove body; one end of the light emitting device is coupled with the upper cover, and extends downwards in the longitudinal length direction substantially; and at least one part of the each light emitting device can be soaked below the liquid surface of the liquid medium.