To clarify the pyrolysis characteristics of straw waste and the correlation with biochar yield in the preparation of biochar, and meanwhile explore the optimal condition for biochar preparation from straw waste, four different types of straw waste were selected to investigate the effects of straw waste type, final pyrolysis temperature, and heating rate on the pyrolysis characteristics and biochar yield of straw waste by thermogravimetric simulation combined with the component characteristics analysis of straw waste. Results show that the maximum weight loss and maximum weight loss rate both appeared at pyrolysis stage, and the order of maximum weight loss rate was: wheat straw>corn straw>rice straw>reed straw, relating to the cellulose content of the four types of straw. Statistical analysis shows that straw waste type, final pyrolysis temperature, heating rate, and retention time all had significant effects on biochar yield of straw waste. The higher the final pyrolysis temperature was, the faster the heating rate and the longer the retention time were, and the lower the biochar yield was. The effects of final pyrolysis temperature and heating rate on the biochar yield of straw were consistent with the thermogravimetric simulation results. According to the pyrolysis characteristics and statistical analysis of biochar yield and energy consumption, the optimal condition of biochar preparation was: heating to 500 ℃ at a rate of 10 ℃/min and keeping for 30 min.