The damage degree of pot seedling in the process of automatic transplanting in dry farming has a direct impact on the survival rate of pot seedling in the later stage. Moreover, the clamping force of pot seedling plays key role in evaluating the damage degree. Aiming at the problems of narrow installation space, improper arrangement of testing equipment to damage seedling or bring back seedling matrix in the automatic transplanter with adjustable clamping force, a clamping force detection system of pot seedling was developed based on piezoelectric film (Polyvinylidene fluoride，PVDF) and signal conditioning technology. The system consisted of PVDF piezoelectric film, special signal conditioning circuit, wireless communication module and signal acquisition software system. The working procedure of the system can be divided into the following steps. Firstly, PVDF piezoelectric film monitored the change of clamping force of seedling claw on pot seedling in real time, and the clamping force was converted into electric charge by piezoelectric effect. Secondly, via the special signal conditioning circuit, the system can implement chargevoltage signal conversion, signal amplification, signal elimination of power frequency, and weaken the vibration and noise generated by ground excitation and transplanter operation. Thirdly, the processed clamping force signal was sent to the signal acquisition software system based on LabVIEW by wireless communication module, and the residual vibration noise was filtered through Kalman filter. The whole system can effectively realize the measurement, indication, storage and warning the clamping force of pot seedling, and assist to reduce the damage rate of pot seedling and improve the success rate of transplantation. In addition, the calibration experiments and laboratory validation experiments were performed to verify the precision and reliability of the system respectively. The calibration experiments demonstrated that the average linear determination coefficient of the clamping force detection sensor was 0.9914, the average sensitivity was 1.0027, and the accuracy was 6.024%. The laboratory validation experiments indicated that the mean and maximum fluctuation ranges of the clamping force measurement values were small, and the standard deviation of the clamping force measurement values of each group were lower than 0.076N, and the output voltage value of the clamping force detection sensor was basically consistent with the variation law of the clamping force during the actual transplanting process. In conclusion, the overall results showed that the developed system had the advantages of high measurement accuracy, low cost and fast response, and can provide a useful reference for clamping force detection of pot seedling in automatic transplanter. 