Laboratory measurements of Ultrasonic P-wave velocities were conducted in weakly compacted sandstone with varying degree of water saturations. We used P wave transducer at frequency 63 kHz and imbibition technique in order to study the influence of water saturation on the P-wave velocity. Our experiment showed that the P-wave velocity (Vp) was reduced significantly at the beginning of the imbibition process. The variations on travel times and the amplitude changes were detected at any degree of saturation. The first and second amplitude of P wave decreased as water saturation (S w) increased in the range of 0.1 to 0.6 in B5 sample, the amplitude increased again afterward. The shifting peaks of the signal that indicated attenuation were also observed in the experimental.