Silk is an important economic fiber, its producing not related only to the method of producing but also preparing processes after productions such as stifling cocoons silkworms. The mechanical performance of dryer locally fabricated using butane gas was tested for stifling cocoons silkworms. The study parameters were the heating air temperature 60, 65, 70 and 75 °C; air velocity through the cocoons 1.5, 2.0 and 2.5 m/sec. and treatment times of 20, 25, 30 and 35 min. These parameters were examined and evaluated on cocoons moisture contents;; cocoon weight; shell weight; shell ratio; stifling pupae's and determination of some quality parameters of silk filament like (length of silk filament; reel-ability of cocoons; tenacity and elongation of silk filaments; and cocoon drying). The obtaned results indicated that, the minimum value of cocoons moisture content was 30, maximum value of cocoons weight, cocoon shell weight and cocoon shell ratio were 2.42g, 1.55g and 68.8% respectively. Stifling pupae's was 100% at decreasing cocoons moisture content to a level less than 45%. Also for quality evaluation tests of silk filament, the maximum value of length of silk filament; reel-ability of cocoons; tenacity and elongation of silk filaments; were 955m, 78.9%, 4.89 g/denier, and 15.78%, respectively.