The Java-Indonesia 500 kV network is the biggest interconnected system in Indonesia. This system extends from the western part of Java Island to eastern part with a distance of approximately 1000 km. This long tie-line may contribute to the instability of power system, in particular, low-frequency oscillation stability of the system at weak grid condition. However, small attention has been paid so far to investigate the low-frequency oscillation stability performance on Java 500 kV system. Hence, this paper investigates the low-frequency oscillation stability performance of Java 500 kV network. Eigenvalue analysis and damping ratio analyses are employed to examine the dynamic behavior of this system. Time domain simulation has been applied to verify the modal analysis of Java system. Furthermore, dual input power system stabilizer (DIPSS) has been applied in this paper to enhance the low-frequency oscillation stability margin of the system. The DIPSS parameters are tuned using Craziness particle swarm optimization (Craziness PSO). From the simulation results, it is found that there is a weak mode in the Java 500 kV system. The installation of DIPSS based on Craziness PSO in the Java 500 system enhanced the low-frequency oscillation stability margin of the system.