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Rice false smut caused by <i>Ustilaginoidea virens</i> is one of the most devastating fungal diseases of rice (<i>Oryza sativa</i>) worldwide. Prochloraz and azoxystrobin belong to the groups of demethylation inhibitors and quinone outside inhibitors, respectively, and are commonly used for controlling this disease. In this study, we analyzed the sensitivities of 100 <i>U. virens</i> isolates from Yunnan, Sichuan, Chongqing, and Zhejiang in Southern China to prochloraz and azoxystrobin. The ranges of EC₅₀ for prochloraz and azoxystrobin were 0.004−0.536 and 0.020−0.510 μg/mL, with means and standard errors of 0.062 ± 0.008 and 0.120 ± 0.007 μg/mL, respectively. However, the sensitivity frequency distributions of <i>U. virens</i> to prochloraz and azoxystrobin indicated the emergence of subpopulations with decreased sensitivity. Therefore, the mean EC₅₀ values of 74% and 68% of the isolates at the main peak, 0.031 ± 0.001 and 0.078 ± 0.004 μg/mL, were used as the sensitivity baselines of <i>U. virens</i> to prochloraz and azoxystrobin, respectively. We found significant sensitivity differences to azoxystrobin among different geographical populations and no correlation between the sensitivities of <i>U. virens</i> to prochloraz and azoxystrobin. Among 887 <i>U. virens</i> isolates, the isolate 5-3-1 from Zhejiang showed moderate resistance to prochloraz, with a resistance factor of 22.45, while no nucleotide variation in the 1986-bp upstream or 1827-bp gene regions of <i>CYP51</i> from 5-3-1 was detected. Overexpression of <i>CYP51</i> is probably responsible for its resistance to prochloraz. Finally, artificial inoculation showed that 5-3-1 was highly pathogenic to rice, suggesting that the resistance of <i>U. virens</i> to prochloraz must be monitored and managed in Zhejiang.