The invention discloses a liquid mixing tank convenient to change a filter screen and relates to the technical field of liquid mixing tanks. The liquid mixing tank convenient to change the filter screen comprises a tank body; a partition plate is arranged at the middle part of an inner cavity of the tank body; a first liquid storage cavity is formed between the upper side of the partition plate and the top of the inner wall of the tank body; a second liquid storage cavity is formed between the lower side of the partition plate and the inner bottom of the tank body; a controller is arranged onthe top of the right side of the tank body; a three-way pipe is fixedly connected to the right side of the tank body; and the two ends of one side of the three-way pipe I are connected with the interiors of the first liquid storage cavity and the second liquid storage cavity in an inserting manner respectively. For the liquid mixing tank convenient to change the filter screen, by forming a throughgroove and an annular groove, through matching arrangement of a pressing block and a pressing rod, the pressing rod is driven to move toward the interior of the through groove in a manner of pressingthe pressing block into the annular groove; and by arranging a compression spring, through matching arrangement of a first fixed ring and a limiting ring, the reset effect of the compression spring to the pressing rod can be effectively ensured.