Based on FPGA with an embedded soft-core MicroBlaze, an information processing system for sun sensor is designed. Soft-core MicroBlaze is employed to implement centroid extraction and attitude conversion. The other resources are used to realize the design of logic modules, such as sun sensor driving, image storage and communication interface. A scan-based centroid extraction algorithm is proposed according to the characteristic of MicroBlaze soft-core. The result shows that the high precision of centroid extraction and attitude conversion is achieved by using single precision floating point number in the MicroBlaze soft-core. The scan-based centroid extraction algorithm process is simple and occupies less resource. In the sun sensor based on System on Programmable Chip (SOPC), co-processors such as DSP or ARM are not needed, so complexity of hardware is decreased and the integrity and performance are improved.