In recent years, photoacoustic tomography (PAT) has caused more and more attention all over the word. As a novel medical imaging modality, it is proved to be non-invasive and high sensitivity. Photoacoustic tomography combines the advantages of both optical imaging and ultrasound imaging, which means high contrast and high resolution. According to the merits of photoacoustic tomography, in our experiments, we used the unfocused transducers with different central frequency such as 2.25MHz, 5MHz, 10MHz, to make photoacoustic tomography research on varisized and diverse target object in phantom, which was used to analyze the influence factors of image resolution. In this paper, we mainly discussed the impact of transducer's central frequency on the image reconstructed results with different experimental samples.