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, to 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 2 kW.