The invention provides a dining table which is simple in structure, does not need splicing and is adjustable in size, and the dining table overcomes the defects in the prior art. According to the technical scheme, the dining table with the adjustable size comprises upper table boards and a lower table board, wherein the two upper table boards are symmetrically arranged on the upper end surface of the lower table board, sliding rails are arranged on the lower end surfaces of the two upper table boards, a first sliding groove is formed in the upper end surface of the lower table boards and matched with the sliding rails, and the two upper table boards can move along the two sides of the lower table board through the sliding rails on the bottom end surfaces of the upper table boards. The dining table with the adjustable size can be widely applied to the technical field of catering.