This paper proposes a new switch box architecture in SRAM-based FPGAs to mitigate soft error effects. In this switch box architecture, the number of SRAM bits required for programming switch box is reduced to 67% without any impact on routing capability of the switch box. This architecture does not require any modification of the existing placement and routing algorithms. The architecture was evaluated based on several MCNC benchmarks using VPR tool. The experimental results show that this architecture decreases the susceptibility of switch boxes to SEUs about 20% on average compared to the traditional ones.