The flow characteristics of the broad-crested side weir considering the levee’s side slope of main channel (ESch) was investigated through hydraulic experiment in order to estimate the discharge coefficient equation. For applicability to actual river, levee’s side slope of main channel 1:0.5, 1:1 and 1:2 were selected. Experimental results show that the new estimated equation for the discharge coefficient including ESch is reasonable and effective in actual applications by comparing estimated and measured discharge over side weirs. Through a multiple linear regression analysis the importance of variabes were ordered as ESch > h/yu > L/yu > Fru. Especially the discharge coefficient equation without Fru was suggested, and the high applicability was reviewed by comparing the measured and calculated overflow of broad-chested side weir.