Abstract: The objective of the study was to establish a rapid and effective technique of inoculating sunflower heads with Sclerotinia sclerotiorum in field condition for screening of resistant resources and breeding for disease resistance. In this experiment , the inoculation period, the best inoculum and its concentration use for inoculation of sunflower head rot in field condition were screened, and evaluate disease resistance in 18 cultivars in the same way. The results showed that three inocula can make the susceptible variety to generate typical heads rot symptom. When the concentration of mycelium content 30.0g/L in PDA (potato dextrose agar medium), or 0.4 g/plate in sorghum grain, It can distinguish resistant differences between sunflower varieties. The same to concentration of ascospore content 1×10³ mL. The effect of inoculation (DSI and morbidity) in beginning flowering to half-bloom stage is better than it in inoculation in full-bloom stage. According to the Orthogonal experiment results show that, ascus spore suspension be inoculum, the concentration of 1×10³ mL, inoculated time is R5.1, and moisturizing for 48 hours were the best conditions of plate rot in filed.At the same time, 4 sunflower varieties were resistant to S. Sclerotiorum be screened out by this technique. The method for evaluation of resistance to S. Sclerotiorum in the field condition can effectively identify the pathogenicity of S. Sclerotiorum and screen the resistance to S. Sclerotiorum for sunflower breeding.