In response to the issues of high intensity, complex operations, and the susceptibility of measurement accuracy to human error in current rice trait analysis, a rice panicle length measurement system is developed based on a self-designed intelligent rice trait analysis platform which integrates the control logic coordinated by PLC and LabVIEW. The Legion Y7000 PC serves as the host computer and the Wecon LX3V PLC operates as the lower computer in this system. The system controls the screw motor to straighten the rice panicle with a force sensor and measures the length of the panicle with a high-precision encoder. Real-time collection, monitoring, and recording of rice panicle length information and force sensor information are achieved. Panicle length measurement tests are conducted on Late Indica 98 and Changnong Japonica 3 rice panicles. The tests show that the system, through the coordinated control of the host computer and the PLC, effectively facilitates panicle stretching, length measurement, and the coordination of various actuators, with an average control response time of 0.8 s. Compared with manual panicle length measurement, the maximum error between the two is between 1.01% and 1.16%. The result shows that there is no significant difference between the two measurement methods. The rice panicle length measurement system can accurately measure the panicle length.