Photon noise squeezing and its physical mechanism of a driven V-type three-level laser are investigated via Scully-Lamb theory.It is shown that intracavity squeezing of 10% and extracavity squeezing of 20% can be achieved.Even if the amount of squeezing in V system is smaller than that in Λ system (intracavity squeezing and extracavity squeezing of up to 50%),both systems have the same mechanism responsible for the squeezing of photon noise.