The present investigation was conducted in October, 2007 at RiceMechanizationCenter, Meet El-Deeba, Kafr El-Sheikh governorate. The modified prototype was fabricated at a small workshop in Kafr El-Sheikh city. The experimental results revealed that the seed cotton extractor (prototype) performance after modification was better than that before. Seed cotton wastage was minimized by 14 and 32.58% for the prototype before and after modification respectively. Also, cotton trash content was reduced by 8.87 and 35.75% for the prototype before and after modification successively. Its productivity was increased by 92.19 and 109.15% before and after modification respectively. Also, the increment in prototype productivity was of 28.24% by increasing feed rate from 0.60 to 0.75Mg/h. At all the investigated feed rates, the modified prototype had higher values of cleaning efficiency than that before. The increment in its cleaning efficiency was of 21.22% by raising feed rate from 0.60 to 0.75Mg/h. The prototype energy requirements were minimized by 42.59 and 47.02% before and after modification respectively. Cotton moisture content was reduced by 31.80% as the drying air temperature was raised by 11.63%. Total cost requirements for the modified prototype were slightly smaller by 0.66% than that before. Whereas, criterion function cost was smaller for the modified prototype by 16.77% than that before modification as seed cotton losses were effectively minimized after modification. The characteristics of cotton fiber quality were highly enhanced and strongly influenced by the investigated variables for the modified prototype than that before its modification.