A small-sized laser proximity fuse based on CPLD was designed for some small-caliber ammunitions, the common anti-interference methods used for medium-caliber and large-caliber ammunitions will not be suitable, due to the limited space and power. Analyzed the interferences of a small-sized laser proximity fuse, the major ones are: (a) the electromagnetic radiation of laser transmitter module; (b) the unstable power supple disturbs all circuit modules; (c) false targets like tree branch. Kinds of technical measures are adopted in circuit design, PCB design, optical system design, and programming to reduce their influences to ensure the necessary stability, reliability and precision. Using small-caliber ammunition as a base to develop prototyping and conduct targeting experiments successfully. The test experiments show that the power consumption is low and it can detect vertical test board (gray iron) at 5 m far away with no more than 90 mA current (25 V DC). The test results in high overload conditions indicate that the prototyping can work normally and steadily in the whole trajectory.