Fly ash (FA) can react quickly in the soil, so that it increases the pH faster and provides the nutrients contained. Using compost in Ultisols soil can increase organic matter, macro and micro plant nutrients, and soil pH. This study aims to determine the combination of the effect of FA and compost on pH, availability of nitrogen (NH4⁺ and NO3^-), phosphorus, and potassium in Ultisols soil. This study used a completely randomized design (CRD) with one factor, the combination of FA and compost, consisted of nine treatment levels, each repeated three times, so that 27 experimental units were obtained. The results showed that the administration of FA and compost had a significant effect on increasing the pH value at the best treatment dose, namely FA (10%) and compost 0 t ha-1 (F₁₀K₀), the administration of FA and compost also had a significant effect on the availability of nitrogen (NH4⁺ and NO3^-) phosphorus and potassium at the best treatment dose, namely FA (5%) and compost 20 t ha-1 (F₅K₂₀).