This article proposes a cybersecurity design scheme for non-classified DCS in High Temperature Reactor nuclear power plants. From the perspective of defense in depth, this article sequentially introduces the non-classified DCS peripheral protection design, build-in security design, and management methods in the cyber-security scheme of the non-classified DCS in High Temperature Reactor nuclear power plants. Firstly, the network architecture of a typical nuclear power plant non-classified DCS is introduced. Secondly, the principles of cybersecurity design for nuclear power non-classified DCS were introduced. Thirdly, the engineering design scheme of non-classified DCS was introduced. When the peripheral protection of the non-classified DCS is breached by an attacker, the non-classified DCS platform will be directly exposed to the attacker. Therefore, a build-in security design scheme for the non-classified DCS has been proposed to improve the protection performance of the non-classified DCS platform by improving its own design. Finally, facing the problems that cannot be solved by the peripheral protection and build-in security of the non-classified DCS, it is proposed to solve them from a management perspective. At the end of the article, the problems in the current cybersecurity of non-classified DCS in High Temperature Reactor nuclear power plants are presented, along with suggestions.