The traditional weak laser coding signal generator has some problems such as large size and poor coding accuracy. A design of hand-held weak laser coding signal generator based on STC15W408AS microcontroller is presented. It solved the problem of the poor timing precision of the traditional microcontroller timer, which requiring high speed complex programmable logic device (CPLD) to assist design. A programmable counter array (PCA) timer mode is used to improve the pulse timing accuracy of the microcontroller to sub-microsecond. The whole machine adopts a single +3.7 V power supply scheme, which can be controlled by buttons or WiFi, with advantages of low power consumption, high precision timing signal and easy to carry and operate.