Objective To get photoacoustic (PA) image of vascular structure inside mouse brain in vivo.Methods A 532nm pulsed laser was used as the pumping source to generate PA signal,and a wide-band PVDF unfocused ultrasound transducer was used to collect time-domain PA signal by circular scan.PA signal recorded at each scanning position was then de-noised by wavelets transform using soft-thresholding.The PA image of the mouse brain vessel was reconstructed by time-domain spherical back projection algorithm.Results PA image agreed well with the histological picture of mouse brain vessel.Conclusion The experimental result indicates the potential value of clinical application.