As a small and low-cost photosensor, the photodiode can be used as low-precision sun sensor alternatively for at least three photodiodes combined, to measure the full sun vector. To obtain the sun vector anywhere providing the continus 360° filed-of-view, it was difficult to choose the number and design the layout of the multiple photodiodes. This paper discretized the 360° field of view as equal surface areas firstly, and transformed the infinite sensor layout optimization problem into a finite combinatorial optimization(nondeterministic polynomial time). Then, the combinatorial optimization problem was solved by establishing the multi-objective optimization function considering the coverage and uniformity and combining the quantum genetic algorithm. The experiment gave the layout effect for the various number and the different field of view of photodiodes, and provided theoretical basis for the optimization of the layout of multiple photodiodes. The experimental results show that the 12-14 photodiodes selected can achieve layout with no coverage and uniform risk nearly.