Abstract: A non-binary irregular repeat-accumulate (IRA) modulation-coded physical-layer network coding (PNC) scheme was proposed for the space two-way relay channels (TWRC) to improve the information exchange rates of space information networks. In the scheme, a same non-binary IRA modulation code was employed at two users. This configuration enabled the recovery of the network coded information sequence from the superimposed signal directly by the relay. The optimized non-binary IRA modulation code was obtained by using extrinsic information transfer (EXIT) chart analysis. Numerical results demonstrate that the proposed scheme can reduce the duration of information exchange by about 48% compared to the conventional time divided multiple access scheme.