The work aims to improve the recycling rate of peanut straw and provide a feasible treatment method for peanut straw fiber to be hot pressed together with wood fiber to prepare adhesive-free fiberboard. Peanut straw was prepared into fiberboard without adding adhesive by hot pressing technology. The single factor experiment was carried out with four factors, namely hot pressing temperature, pressure, time and peanut straw addition amount, and then the process was optimized by the three-factor and three-level response surface experiment. The response surface model P<0.01, lack of fit P=0.4896>0.05 and model regression coefficient R2=0.9867. After the response surface was optimized, the optimal process condition was obtained as follows: the hot pressing temperature was 170 ℃; the hot pressing pressure was 8 MPa; the hot pressing time was 6 min and the mass fraction of peanut straw was 20%. Under these conditions, the MOR value was the largest, which was 10.1815 MPa. The regression model reaches the extremely significant level, but the model out-of-fit degree is not significant, which indicates that the model correlation degree is good. The MOR value obtained by the verification test under the optimal process condition is (10.182 33±0.157)MPa, which is close to the predicted value, indicating that the optimized process is reliable.