Aiming at the application of large amount of data interaction between processing system and programmable logic in system of chip, a data interaction method between PS and PL based on double data rate synchronous dynamic random access memory is proposed. PS and PL interact with each other according to the custom protocol by accessing the common DDR. The space for data interaction in DDR is divided into instruction space and data space. PS and PL control their reading and writing processes by reading and writing instruction data in instruction space and analyzing the information they transmit according to the protocol. PL accesses DDR through high-speed on-chip bus, and PS uses memory read-write tools to read and write DDR. The test results show that the interaction method has the advantages of high speed, less logic resources and convenient use. The data interaction speed can reach 88MB/s. It is suitable for the application scenario where PS and PL need to interact a large amount of data in real time. It has been successfully applied in the vehicle real-time high-precision positioning system based on three-dimensional lidar.