The invention provides a method for improving sensitivity and linearity of a latex reagent, and belongs to the field of medical test. The method comprises the following steps: step (1), preparing a solution A: the solution A includes a monoclonal antibody connected to a latex microsphere for an antigen to be tested; step (2), preparation a solution B: the solution B includes phenylalanine, lysineand vitamin C; and step (3), mixing the solution A obtained in step (1) and the solution B obtained in step (2) to obtain a solution C, wherein the solution C is used for detecting the antigen to be tested. The invention further provides a preparation method of a detection kit, wherein a certain amount of the solution B is added to a reagent R2, and the addition of the solution B not only improvesthe sensitivity of the detection, but also can obviously improve the linear relationship of the detection; and the addition of the solution B is unexpectedly found to improve the stability of the reagent R2, and the stability of the reagent R2 is still relatively high under the condition that a preservative does not need to be added.