This paper presents results of research performed to identify optimum mix proportions for production of flowable fill with high volume fly ash content. The fly ash used in this study met the requirements of KS L 5405 and ASTM C 618 for Class F material. Tests were carried out on concrete designed to have 10 ~ 15kg/㎠ compressive strength at the 28-day age with fly ash contents of approximately 280kg/㎥. Slump was held at 25±1cm for all mixtures produced compressive strengths at 28 days were found to range from 5.03 to 13.69kg/㎠.