Silicon dioxide (SiO₂) is an important component of nuclear reactor optical fiber and is also a candidate material for wast solidification. Owing to its special physical and chemical characteristics, it is used in many different technology fields like optics, electronics, energy orspace. Swift heavy ion irradiation can modify the crystal structure and optical property of optical material SiO₂. Swift heavy ions deposit their energy mainly by inelastic interaction. Highly ionized lattice atoms may be formed along the trajectory, and a fraction of their electrical energy can be converted directly into the kinetic energy of the ions. The irradiation experiment is performed with Xe^q+ ions at the irradiation terminal of the sector-focused cyclotron at heavy-ion research facility in Lanzhou (HIRFL). The on-line spectral measurement experiment is carried out during irradiation. In the darkroom, the UV-visible light emission from the target is focused into optical fiber by a collimating lens, and then is analyzed with the Sp-2558 spectrometer equipped with a 1200 g/mm optical grating blazed at 500 nm. In the present work, SiO₂ single crystals are irradiated with 93–609 MeV Xe^q+ ions with a dose in a range of 1×10¹¹–3×10¹¹ ions/cm². During irradiation, the emission spectra, in a range of 200–800 nm, from SiO₂ irradiated by 93, 245, 425 and 609 MeV Xe^q+ ions, are obtained. Two emission bands centered at 461 and 631 nm are observed. These emission bands are produced by Frenkel exciton radiation de-excitation and their intensities are closely related to the irradiated ion energy and radiation dose. The results show that the light intensity increases with the electron energy loss index increasing. And owing to crystal damage caused by ion irradiation, the intensity of emission spectrum decreases with the augment of irradiation dose. Ion loses its energy throughout the ion track via Sn and Se interacting with target atoms and electrons respectively, and the energy lost by the ion is estimated by using SRIM code. The SRIM simulated ion ranges and recoil atom distribution, target ionization (energy loss to target electrons), damage production in SiO₂ are presented. Based on the energy deposition process, the emission bands related to the crystal structure itself are discussed. It indicates that electron energy loss plays a leading role in the process of light emission. In-situ measurement of the optical emission is of great significance in studying the irradiation modification and can help to understand the process of crystal damage caused by ion irradiation.