ABSTRACT The research about the effect of rice husk ash (RHA) grain size has been conducted for compressive strength and porosity of composite ceramic based on clay-iron sand-rice husk ash by using grain size variation of rice husk ash for: 70 mesh, 100 mesh, and 140 mesh. The objective of study to find out of compressive strength value of composite ceramic based on clay-iron sand-rice husk ash by variation of rice husk ash grain size, and find out of the porosity effect concerning compressive strength composite ceramic clay- iron sand-rice husk ash. The sample was made about 50 mm x 50 mm x 50 mm, with the composition of clay, sand iron, rice husk ash are (75%:25%:5%) and the compressive strength was done by ASTM C-67 standard. From this research was known that the lowest porosity value was showed by ceramic sample which using rice husk ash 70 mesh grain size as 37,47 %, while the biggest porosity was showed by ceramic sample which using rice husk ash 100 mesh grain size as 45,2 %. The highest compressive strength was showed by ceramic composite sample clay-iron sand-rice husk ash which using 70 mesh grain size as 11,85 MPa, while the lowest compressive strength was showed by 140 mesh grain size as 6,02 MPa. The dissent of compressive strength was resulted when rice husk ash milling, then it was increased concentration of SiO2 in the sample, so the compressive strength was decreased. There for the ceramic composite clay-iron sand-rice husk ash could be using for construction sector for load bearing walls. Keywords: clay, sand iron, rice husk ash, XRF, SEM, XRD, porosity, compressive strength