The effect of hydrogen-donor on the cracking of thermosetting plastic was examined in the presence of diesel and polypropylene with a reaction time of 3 hours at 350-450 ℃ in a 1000 ml autoclave under initial nitrogen atmosphere. Phenol resins as a typical thermosetting resin (plastic), showed 40.56 wt% decomposition and about 38.77 wt% yield of distillable oil when diesel was used. With PP, the decomposition rate decreased to 32.82 wt%. Diesel was an more effective hydrogen-donor than PP for the thermosetting plastic cracking.