A study of using crude bromelain enzyme in producing hydrolysed protein liquid from scad (Decapterus) aims to produce a high nutritional value, safe and hygiene product with the highest recovered yield to contribute to diversification of food from scad and increase economical value for scad materials. Total five main experiments were conducted to study on the five main factors effecting on the product quality thence finding out the best procedure to produce the best product: (i) Studying on the effect of the time for grinding (5, 10, 15 and 20 minutes), (ii) the effect of crude bromelain enzyme at different rates (2, 3, 4 and 5%), (iii) the effect of hydrolysis temperature (45, 50, 55 and 60oC), (iv) the effect of hydrolysis time (1, 2, 3 and 4 hours) and (v) the effect of pH levels (4, 5, 6 and 7) on the product quality. The results showed that the best procedure in which the time for grinding 15 minutes, the rate of crude bromelain enzyme 4%, the hydrolysis temperature 55oC, the hydrolysis time 2 hours and the pH 5, produced the product of hydrolysed protein liquid from scad with the highest total amino acid contents (5.367 g.L-1), the ratio of total amino acid to total nitrogen (34.3%), the highest recovered yield (73.8%) and the lowest ammonia- nitrogen content (0.260 g.L-1).