Traffic simulation model is an effective approach to analyze traffic operation supported by its capability of providing the real condition resemblances relative output. A case study was conducted at SAMSAT Yogyakarta roundabout Yogyakarta it was fundamentally concerned after its performance which is crossed by many kinds of vehicle namely; becak, bicycle, motorcycle, car, bus et cetera. It is important to be taken seriously remembering the high traffic’ flow as an effect and a line of traffic jam at peak hours. The objectives of this study are to analyze the existing condition and to offer alternative solutions to improve roundabout performance by using VISSIM 9.0 software. The result obtained regard performance amongs other: the average delay value as 15,85 seconds, average queue length as 277,12 meters and level of service as C. in able to improve existing condition, it is recommended 2 alternative solutions: 1) Employing APILL at roundabout and 2) traffic roundabout’s diameters’ decrease and road widening at section C and D. Result of 5 times alternative trial are: 1) APILL installation, chosen from the best, results average delay value as 56,28 seconds, average queue length as 318,02 meters and level of service as E, 2) traffic roundabout’s diameters’ decrease results average delay value as 15,74 seconds, average queue length 20,44 meters and level of service as C. The result of this study showed that alternative number 2 is the best to improve crossroad performance that is traffic roundabout’s diameters’ decrease and section widening at Tentara Pelajar Utara street and Suryonegaran street.