The large laser gyroscope based on Sagnac effect is the core equipment for measuring earth parameters.Compared with the small inertial navigation gyro,the large laser gyro improves the sensitivity and stability of speed measurement by 6 orders of magnitude,and the performance improvement makes it possible for the new applications of the large laser gyro in the fields of geophysics,geodesy and seismology.The large laser gyroscope introduced in this paper is an important technical means to study the measurement of earth orientation parameters (EOP)at present.Compared with the large number of successful applications of large laser gyros abroad,the development and application level of large laser gyros in China still needs to be improved constantly to meet the demand of high precision measurement of earth rotation angular velocity and calculation of universal time (UT1).