Abstract: To verify the effectiveness of its energy conservation of on-load automatic capacity regulating distribution transformer and the mechanism of solving transformer running in “ oversized power”. According to the measured dynamic day and month load data, the daily load curve and monthly load curve is plated. Then the dynamic power consumption of SZ11-M-T on-load automatic capacity regulating distribution transformer and S11 distrbution transformer is calculated and the comprehensive economic benefit is comparised too. The results show that the effective way to avoid transformer running in “ oversized power” is to use on-load automatic capacity regulating distribution transformer for aera whose power consumption significantly different from peak to valley, region whose peak and valley loads frequently rotate and rural aeras whose power consumption is seasonal concentration. Energy conservation of on-load automatic capacity regulating distribution transformer is obivously profitable