A coded modulation scheme for deep-space optical communications is proposed,which is composed of an outer singleparity-check(SPC)-based product code,an interleaver,a bit-accumulator and a pulse-position modulation(PPM).It is referred as SPC-APPM code,which is decoded with an iterative demodulator-decoder using standard turbo-decoding techniques.Investigations show that the scheme has the advantages of low encoding and decoding complexities,good performance and flexible code rate for all rates above 1/2.Meanwhile,simulation results demonstrate that the SPC-APPM provides the performance similar to the low-density parity-check-APPM(LDPC-APPM),superior to the LDPC-PPM and product accumulate code-PPM(PA-PPM),although inferior to serially concatenated PPM(SCPPM).At the bit error rate(BER) of 10-5,the performance of SPC-APPM is about 0.7 dB better than LDPC-PPM and 1.2 dB better than PA-PPM. A coded modulation scheme for deep-space optical communications is proposed, which is composed of an outer single parity-check (SPC) -based product code, an interleaver, a bit-accumulator and a pulse-position modulation (PPM) as SPC-APPM code, which is decoded with an iterative demodulator-decoder using standard turbo-decoding techniques. Investigations show that the scheme has the advantages of low encoding and decoding complexities, good performance and flexible code rate for all rates above 1/2 .Meanwhile, simulation results demonstrate that the SPC-APPM provides the performance similar to the low-density parity-check-APPM (LDPC-APPM), superior to the LDPC-PPM and product accumulate code-PPM (BER) of 10-5, the performance of SPC-APPM is about 0.7 dB better than LDPC-PPM and 1.2 dB better than PA-PPM.