On April 28th, 2025 Power systems in Spain and Portugal suffered stability destruction and massive blackout. The total power outage duration exceeded 18 hours, affecting the power supply for over 50 million people. The power system overview for Spain and Portugal, including the generation, power network and load profiles, are firstly introduced in this paper. Then, the entire development process of failure and blackout are presented based on the blackout investigation reports provided by the Spanish government and the Spanish power system operator, covering the system operation status before the fault, the failure progression, and the system restoration phases, and the causes of the blackout are summarized. Finally, based on the actual situation of power systems of China, suggestions are proposed for preventing large-scale power outages in the context of high penetration of renewable energy.