| To prepare 25% thiamethoxazine carbendazim pyraclostrobin suspension concentrate(25% thi car pyr FS) for cotton seeds treatment for direct seeding, the main additives in the formulation were screened by flow point method and orthogonal design. The soluble starch-styrene binary copolymer film former was synthesized and the performance of the film former was determined. The quality index of 25% thi car pyr FS was determined and its effect on cotton seed germination rate, seedling chlorophyll content and free proline content was evaluated. The active ingredients thiamethoxazine, carbendazim, and pyraclostrobin accounted for 10%, 10%, and 5%, respectively. The mass fractions of wetting and dispersing agents W600 and D800 were 2.5% and 4.0%, respectively and the mass fractions of viscosity modifiers xanthan gum and magnesium aluminum silicate were 0.18% and 0.30%, respectively. The mass fraction of antifreeze glycol was 5%, of color paste Haishu liquid red 2R 2%. The viscosity of thi car pyr FS was 204.21 mPa?s, the particle size D90, D50, D10 were 1.25, 0.82, 0.35 μm, the centrifugal sedimentation rate was 8.34%, the suspension rate was 96.02%, the water extraction rate was 4.72%, and the shedding rate was 3.35%. The film forming time of the film former was 11.33 min, and the uniformity of coating was 91.67%. When the drug to species ratio was 1∶50, the germination rate was 95.67%, under which the germination rate increased by 1.78%, the chlorophyll content of cotton seedlings increased by 70.54%, and the free proline content increased by 77.55%, compared to the blank control. The prepared seed treatment suspension 25% thi car pyr FS has good film formation stability, and is safe to cotton seeds, which can ensure high germination rate and promote the growth and development of cotton seed.