In view of the problems such as the complex secondary circuit wiring of the traditional generator-transformer group protection, non-unified external interface standard, inconvenient operation and maintenance, and the higher requirements on the protection data processing, communication data processing and adaptive operation and maintenance mode, this paper presents a design scheme of protection device based on analog quantity using the conventional sampling and switch quantity using the GOOSE transmission. It summarizes and studies the key technologies of the device system, such as comprehensive optimization technology of generator differential protection, abnormal data fault-tolerant technique, generator protection algorithm based on asynchronous sampling for different working conditions, and intelligent operation of protection device operation and maintenance, and puts forward the whole project configuration scheme of the generator-transformer group protection of the large scale smart hydropower plant. The theoretical simulation and test results show that the scheme can meet the technical requirements of relay protection for intelligent hydropower station. This work is supported by Science and Technology Project of State Grid Corporation of China (2016).