The adjacent frequency jamming caused by the complexity of the network can easily reduce the sensitivity and even block the broadband system. To tackle this issue, this paper apply the transmissive reconfigurable intelligent surface (TRIS) to assisted broadband system for space-frequency joint anti-jamming. Precisely, a space-frequency joint anti-jamming model for broadband system is established, where TRIS is functioning as a filter to eliminate adjacent frequency jamming from both spatial and frequency domain. To mitigate jamming effectively, an optimization problem to design TRIS phase shift and transmitter precoding is formulated in the case of known incomplete illegal channel state information. Due to the non-convexity and intractability of the original problem, we further propose an alternating optimization (AO) algorithm to solve it efficiently. Simulation results show that the proposed scheme can form a filtering effect of exceeding 10 dB on the adjacent frequency jamming signal and enhance the desired signal in a certain extent, which effectively improves the anti-jamming ability of the system.