The invention provides an irradiation distance measurer and an implementation method thereof. The irradiation distance measurer comprises a KS103 ultrasonic ranging module, a singlechip control module, a display module, an alarm module and a power supply module which are electrically connected and is implemented by taking C language as software programming language in a query waiting manner; and the irradiation distance measurer has the characteristics of low power consumption and high precision and is simple and convenient to operate, reliable in performance, high in precision, small and portable, capable of correcting the measurement error caused by temperature and suitable for various radiant therapeutic instruments, such as laser, infrared rays and microwaves and measurement of distance between patients so as to promote the therapeutic quality, ensure therapeutic effect and prevent medical accidents from happening.