Abstract: Phoma herbarum SYAU-06 isolated from diseased leaves of dayflower was expected to be a candidate of mycoherbicide, which could cause the death of dayflower by effective infection and was safe to most crops. In this study, the biocompatibility of different carriers and adjuvants with P. herbarum was explored. Under the conditions safe to SYAU-06, the physicochemical properties of different carriers and adjuvants were compared. The optimum formula for P. herbarum SYAU-06 water dispersible granules (WG) was determined as follows (by mass fraction): SYAU-06 fermentation mycelial cultures 15%, wetting agent BX 6%, dispersant NNO 4%, disintegrating agent ammonium sulfate 6%, binder polyethylene glycol (PEG 4000) 4%, stabilizer calcium carbon 5%, carrier silica 60%. The properties of P. herbarum SYAU-06 WG prepared in accordance with this formula were measured. The results showed that the content of SYAU-06 living mycelium was 2.55 × 10⁸ cfu/g, the wetting time was 28.16 s, the disintegration time was 70.50 s, the suspension percentage was 88.90%, the pH value was 6.97, and the moisture content was 1.47%. All of the indicators of the sample were up to the standard. The field control efficacy of P. herbarum SYAU-06 WG on dayflowers in soybean field was determined by the foliage spraying method. The fresh weight control effect against dayflower 21 days after the application was 50.89%, 55.97%, 60.67% and 69.88% respectively at the formula dosage of 1305, 1740, 2175 and 3480 g/hm².