Soybean protein hydrolysate was used to manufacture non-fat set yoghurt, it was added to milk in a range between 3-20%. Results showed that the best ratio of soybean hydrolysate to be used as fat substitute to manufacture non-fat yoghurt was 5% and 10% respectively. Addition of soybean hydrolysate decreased the coagulation time of yoghurt samples; the higher decrease was noticed when 10% of soybean hydrolysate was used, the coagulation time decreased from 4.20h to 3.15h.  Addition of soybean hydrolysate to skim milk increased the growth of both probiotic bacteria and yoghurt culture, and also improved the water holding capacity of produced yoghurt. Addition of 10% soybean protein hydrolysate increased the quantities of acetaldehyde from (15.41-27.50ppm), diacetyl from (0.116-0.171expressed as O.D at 540 nm), and acetoin from (0.159- 0.220 expressed as O.D at 540 nm). Addition of 5% soybean protein hydrolysate increased the acetoin content from (0.144 ± 0.002-0.160 ± 0.002 expressed as O.D at 540 nm). Storage of yoghurt samples for 7 days increased the amount of acetoin produced from (0.160 ± 0.002 to 0.239 ± 0.002 expressed as O.D at 540 nm) when 5% soybean hydrolysate was added. So, non-fat yoghurt with 5% soybean hydrolysate could be used for the manufacture of acceptable bio-yoghurt. Finally, the addition of 5% soybean protein hydrolysate improved the sensory properties of set-style yoghurt.