Crosstalk is the key parameter affecting the imaging quality of high-density photodiode array for imaging applications. The characteristics of electrical crosstalk of the 100μm back-illuminated PIN linear array were analyzed, and simulations on the dark current and photo current of the array cells were carried out with Silvaco TCAD software. The effects of guard ring on the dark current and electric crosstalk of the devices were studied comparatively. The results show that the dark current of PIN photodiode arrays with guard ring is superior to that of the devices with no guard ring structure; the electrical crosstalk of the PIN arrays with guard ring is only 1/5 of that of PIN array with no guard ring.