The atomic fountain clock is one cold atom applied apparatus possessing important applications. Compact laser system design is one of the key techniques for a portable cold atomic fountain clock. This paper introduces a gridded optical platform built with the general aluminum profiles, and based on it, we construct a compact optical path for the ⁸⁵Rb fountain clock. Through simulation, it is proved that the profile gridded platform has better mechanical properties in two-dimensional direction. On this platform, we design and build the modules of such as four-pass frequency shift, injection locked amplifier, cooling optical path, repumping and probing paths to satisfy all requirements of an atomic fountain clock. The platform covers an area of 50 cm×50 cm and has a height of 2.5-3 cm. The optical path has been running continuously for more than 8 months with a power fluctuation less than 5%. Based on the compact optical system, we have completed the subsequent physical and microwave experiments of ⁸⁵Rb fountain clocks.