The science data generated by five instruments onboard the space solar telescope is about 1728GB per day.Data flow passes through the onboard data handling system with the data storage unit called the solid state recorder as the core element to be buffered,compressed,stored and down-linked.The requirements for the solid state recorder were analyzed,the state machine model was made,which could reduce the system design in complexity,and the whole scheme was established.A ground functional prototype was completed according to above scheme with DSP and FPGA as the control part,and the DRAM chip array as the storage module.The system functions were emulated and proved.