The traditional control strategy used for a CLLC resonant converter is the pulse-frequency-modulation(PFM) control method. However, the precise mathematical modeling process for a CLLC resonant converter using PFM control under light-load conditions is difficult, posing challenges for achieving accurate synchronous rectification(SR). Therefore, this paper proposes a precise time-domain multi-mode SR strategy for CLLC resonant converters under various light-load conditions. This time-domain approach develops accurate time-domain formulas for the resonant variables in different operating modes, thereby enabling accurate calculation of the SR angle for the CLLC resonant converter under various light-load conditions. Furthermore, facilitate the implementation of the SR method in digital controllers, an SR angle fitting method is applied in this paper. Additionally, the practicality of this proposed light-load SR method is confirmed through an experimental platform with a rated output power of 2kW.