A field experiment was conducted at Jimma Agricultural Research Center since the 2017 cropping season to evaluate the effect of NPSB fertilizer rate kg ha-1 (0,100,159,214, and 239) on proximate composition of three orange- fleshed sweet potato varieties (Kulfo, Tulla and Guntutie). The experiment was arranged in 3 X 5 factorial RCBD with three replications. Data on proximate values were collected and subjected to SAS data analyses. Results revealed that the main effects of varieties were highly significant influenced flour moisture content, fat, crude fiber, ash, crude protein, utilizable carbohydrate (P<0.01). Flower moisture content was highly significantly different in variety Guntutei (6.99%); however, it was statistical parity with Tulla (6.66%) variety. The least was scored by Kulfo (6.43%). Fat content was a highly significant difference in the variety Kulfo (1.45%) and found in the ranges of 1.28% to 1.45%. Crude fiber content was highly significantly different in variety Kulfo (6.99%) and the least was scored by variety Guntutei (6.20%). Ash content was a highly significant difference in variety Kulfo (4.67%) and the least was scored by variety Tulla (4.24%). Crude protein content was a highly significant difference in Variety Tulla (9.72%) and the least was scored by variety guntutei (8.36%). Utilizable carbohydrate content was a highly significant difference in variety Guntutei (72.6%) and the least was scored by variety Kulfo (71.26%). The main effects of NPSB rates were highly significant influenced crude fat, crude fiber, ash, crude protein, utilizable carbohydrate and gross energy (P<0.01). The interaction of varieties with NPSB blended fertilizer levels resulted in a significantly high difference in flour moisture, crude fat, crude fiber, ash and crude protein, utilizable carbohydrates (P<0.01). Flour moisture content was significantly highest different in variety Guntutie with 214 kg ha-1 (7.80%). The highest significant fat content was observed in variety Kulfo with 100 kg ha-1 (2.01%) and Guntutei with 159 kg ha-1 (2.04%). Crude fiber content was significantly highest different in variety Kulfo without fertilizer (8.99%). Ash content was significantly highest in Kulfo with 239 kg ha-1 (5.12%) NPSB blended fertilizers. Crude protein content was significantly highest in Tulla without fertilizer (12.64%). The mean of utilizable carbohydrate was recorded as significantly highest different by variety Tulla with 100 kg ha-1 (74.99%) and Guntutei with 159 kg ha-1 (74.83%). In conclusion, Kulfo variety was recommendable for its highest fat, fiber, and ash while Tulla for its protein content either alone or interactions with NPSB fertilizer rates.