A total number of 1200 Avian unsexed day old broiler chicks was randomly assigned into completely randomized 2 X 3 factorial, with 4 replicates per treatment. The chicks were subjected to chronic sever or mild heat stress and fed commercial diet (Control) containing 23 and 21.5% crude protein and 3125 and 3050 Kcal ME /Kg for starter and grower diets, respectively , drink water supplemented with 0.3% KCl  (KCl) or fed commercial diet supplemented with 1g ascorbic acid /1Kg feed (AA).  The objective of the study was evaluating the validity of using KCl and AA supplementations as relieving agents from heat stress for broiler chicks reared in hot arid environment. Following parameters: body weight, daily gain, feed intake, feed conversion,  mortality and carcass parts and edible muscle composition were studied. The results indicated that supplemental KCl under severe heat stress increased body weight and daily gain, decreased mortality percentage and increased wing weight compared to the control group. However, under mild heat stress supplemental KCl decreased body weight, daily gain, decrease feed intake, increased neck weight and abdominal fat, decreased inedible parts weight and decreased protein content in edible muscles compared to control group. Supplemental AA under severe heat stress decreased mortality percentage, increased carcass and neck weights, decreased inedible weight, increased protein and decreased fat contents in edible muscles compared to control group. Under mild heat stress, supplemental AA decreased body weight, daily gain, feed intake, inedible part weights, increased neck and abdominal fat weights, decreased protein and fat contents of edible muscles compared to control group. It could be concluded that supplemental KCl was better than AA to be recommended for broiler chicks under severe heat stress to improve the performance.