A probabilistic shaping passive optical network (PON) based on symbol-level labeling and rhombus-shaped modulation is proposed in this paper, which indicates optical access network can be deployed in a flexible and robust way with reasonable costs. Energy efficiency is also achieved significantly. An experiment that demonstrates probabilistic shaping PON data transmission over 25 km standard single-mode fiber (SSMF) with CAP (carrier-less amplitude and phase) modulation is successfully conducted. Results show that the received optical power has improved by 2 dB at the threshold of 1×10-3 BER compared with the conventional 16-CAP, which suggests the superiority of our proposed scheme in next generation PON.