Rice husk is one of the biggest wastes from rice production. Rice husk can be used as an alternative in producing silicon dioxide (SiO2). Silicon dioxide is widely used in various industries, such as glass, ceramics, tires and electronics. In this paper, charcoal from rice husks is annealed at various temperatures of 800 °C, 850 °C and 900 °C and then characterized using FTIR. In previous studies, analysis using FTIR was able to show the functional groups of Silicon dioxide found in rice husk charcoal. FTIR data modified with the Kramers-Kronig (KK) equation can produce Longitudinal Optics (LO) and Transverse optics phonon (TO) values. The LO and TO values are the optical properties of the Silicon dioxide from rice husk charcoal. In addition, the value of the dielectric function can also be obtained. Based on the results, it shows that the LO values for each treatment were 907.47 cm−1, 958.62 cm−1, and 986.67 cm−1. The TO values for each treatment were 903.61 cm−1, 954.00 cm−1 and 964.41 cm−1. The dielectric function values of each treatment were 512.00 cm−1, 962.48 cm−1 and 1007.00 cm−1. By analyzing the optical-phonon parameters of Transverse Optics (TO) and Longitudinal Optics (LO), we succeeded in characterizing the SiO2 properties with the variations of annealing temperature. We determined that the TO and LO were not-monotonously affected by the variation in annealing temperature, which was determined by studying the optical-phonon wavelengths.