In the current era of highly developed science, technology and technology, the demand for natural fabrics is increasing year by year in the world market, and the world silk industry and science are led to the cultivation of mulberry varieties with high nutritional value and the creation of breeds and hybrids suitable for different seasons of the changing external environment. In recent years, in the Republic of Uzbekistan, the practice of rearing mulberry silkworms several times a year has been used. However, there are no breeds and hybrids suitable for the hot summer conditions of our country, based on this, scientific research has been started in the direction of creating heat-resistant breeds at the Silk Research Institute. In this article, the results of the breeding of 6 breeds and 4 different industrial hybrids of mulberry silkworm under hot conditions are described. Based on preliminary data, Line 1 and Line 2 systems were found to have high embryonic and post-embryonic viability under hot summer conditions. However, the average cocoon weight of these systems was 1.68-1.73 g, cocoon shell weight was 339 mg, and cocoon silkiness was 19.6-20.2%. Based on the obtained results, it was concluded that Line 1 and Line 2 systems can be used as initial selection material for creating heat resistant breeds.