The invention discloses a high-precision full-dry ultrasonic bone 
densitometer. The bone 
densitometer consists of an ultrasonic parameter measuring unit, a sensor unit and a bone 
densitometer mechanical driving unit. The ultrasonic parameter measuring unit comprises a control communication module, a time measurement module, an ultrasonic transmitting / receiving switching module, an 
ultrasonic excitation module, an ultrasonic receiving module and a transmitting and receiving probe set module. Two transmitting and receiving probes are adopted for measuring the widths of soft tissues on the two sides of the 
calcaneus respectively, and a timing 
chip is adopted for timing; and the width difference of the soft tissues of the 
calcaneus and the error of the sound velocity difference of the soft tissues and the 
calcaneus are eliminated. A temperature sensor measures the 
body surface temperature of the calcaneus part, the sound velocity of the soft tissues of the calcaneus is corrected according to the 
body surface temperature, and the measuring precision is improved. Each transmitting and receiving probe is provided with a thin 
film pressure sensor, and the consistency of the clamping force of the calcaneus is guaranteed. A 
ball screw pair and a two-way guide rail transmission structure are adopted, and the 
central symmetry of the motion of the transmitting and receiving probes is guaranteed. A 
solid-state 
coupling auxiliary probe generates an 
ultrasonic transmission channel, and the measuring precision is further improved.