A high denitrification shared type Orbal oxidation ditch, pertaining to water treatment technical field, comprises an outer channel, a median channel, an inner channel, all of ellipse, and a secondary deposition tank. Wherein, the length of the outer channel is prolonged in the ellipse's major axis direction and the secondary deposition tank that is tangential to the inner wall or shares the wall with the outer channel is arranged between the outer and median channels. All the channels (the outer channel, the median channel and the inner channel) and the secondary deposition tank are integrated in the Orbal oxidation ditch, all of the anaerobic zone, regulation zone, hydrolysis acidifying zone, primary deposition zone, sludge outer re-circulation zone and wastewater inner re-circulation zone etc. can also be arranged in other space, in this way, to reduce the area occupied and the investment cost for the entire equipment to the minimum values, prolong the residence time in the oxidation ditch remarkably and make the total denitrification efficiency very high.