Objective A new type of ultrasonic diagnostic apparatus was used to evaluate the cardiac functions of rats by two-dimensional and M-mode echocardiography, and the feasibility and accuracy of this method were assessed. Methods A new type of ultrasonic diagnostic apparatus with a probe frequency of 6 MHz -19 MHz was applied. The left ventricular structure and various indexes were detected by transthoracic ultrasound after anesthesia in six normal male SD rats. Results Transthoracic echocardiography clearly showed the general structure of the rat heart, and accurately and stably obtained the cardiac function parameters of the left ventricle of rats, which can be used to evaluate the cardiac functions of rats. Conclusions High-quality rat cardiac gross structural images, and stable and reliable cardiac function data can be obtained using this new ultrasonic diagnostic apparatus. It is a non-invasive method for continuously and accurately examining the gross structure of the rat heart and evaluating the cardiac functions.