The invention belongs to the technical field of ceramic materials, and particularly discloses a dense ceramic gelcasting method based on low-concentration agarose and low-solid-content slurry. The method includes the steps that ceramic powder, dispersant and agarose are added into water at a time to be prepared into mixed suspension slurry with the solid phase volume fraction of 20-30% and the agarose concentration of 1.3-2.5wt%; then, after the pH of the mixed suspension slurry is regulated to be 10, the mixed suspension slurry is subjected to ball milling, defoamed and injected into a mould for heating treatment in sequence, after the mould is cooled naturally, drying is carried out in multiple steps, and a green body is obtained; finally, sintering is carried out, and ceramic with the density of 95-99% is obtained. According to the method, all the raw materials are prepared into the mixed suspension slurry with a low solid content and a low agarose concentration at a time, ball milling and vacuum defoaming are directly carried out, the mixed suspension slurry does not need to be stirred after being poured into the mould, it can be avoided that foam is carried in and influences the density of the ceramic, and a good defoaming effect and high defoaming efficiency can be achieved; besides, due to the ultralow agarose concentration, the extremely small agarose use amount and the low solid content of the ceramic slurry, the sintering cost of the high-density ceramic is low.