An integrated passive reactor system including a pressure vessel, a containment vessel arranged outside the pressure vessel, and a reactor core arranged inside the pressure vessel. A primary loop operates in full natural circulation. The reactor system is provided with a secondary side passive residual heat removal system including a primary loop heat exchanger arranged inside the pressure vessel and a passive residual heat removal heat exchanger arranged outside the containment vessel. The primary loop heat exchanger is arranged above the reactor core. The passive residual heat removal heat exchanger is arranged inside a water tank which is fixed outside the containment vessel. The primary loop heat exchanger and the passive residual heat removal heat exchanger are connected by heat exchanger inlet pipelines and heat exchanger outlet pipelines.