A novel method for time synchronization of bistatic radar system is put forward based on two-way time transfer via troposphere scattering (TWT3S).In order to get accurate time difference of the radar stations, the troposphere scattering communication equipments are employed to contrast bilateral time signals.Firstly, the calculation model of TWT3S is deduced in detail.Then the time interval measurement error, the launching and receiving device delay error, the tropospheric delay error and the geometrical distance error are studied.Finally, theoretical precision of TWT3S is presented.The computational results demonstrate that tropospheric delay error is the main error, which accounts for more than 90% of all errors.Further more, theoretical precision of TWT3S system is 15~21 ns, and obviously it has a better performance compared with the direct synchronization method via microwave or optical fiber channel.The work provides a new way for time synchronization of bistatic radar system.