A high-sensitivity and large-capacity free space optical (FSO) communication scheme based on the soliton microcomb (SMC) is proposed. Using ultra-large bandwidth stabilized SMC with a frequency interval of 48.97 GHz as the laser source, 60 optical wavelengths modulated by 2.5 Gbit/s 16-Pulse position modulation (PPM) are transmitted in parallel. A corresponding outfield high-sensitivity 150 Gbit/s FSO communication experiment based on the SMC was carried out with 1 km space distance. Our experimental results show that the best sensitivity of the single comb wavelength which has higher OSNR can reach -52.62 dBm, and the difference is only 1.38 dB from the theoretical limit under the BER of 1 x 10-3 without forward error correction (FEC). In addition, at BER of 1 x 10-3, 16-PPM has a higher received sensitivity of 6.73dB and 3.72dB compared to on-off keying (OOK) and differential phase shift keying (DPSK) respectively. Meanwhile, taking the advantage of multi-channel SMC, 60 x 2.5 Gbit/s can achieve 150 Gbit/s large-capacity free-space transmission. For comparison, commercially available single-wavelength laser based FSO communication system have also been performed in the outfield. The outfield experimental results demonstrated the feasibility of high-sensitivity, large-capacity PPM FSO communication based on SMCs and provided a new perspective for the future development of large-capacity, long-haul FSO communication.(c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement