1. A particle filter, suitable for performing particle filtering on a frame, for tracking an object in the frame, wherein the frame has a plurality of image blocks, the particle filter comprising: a frame cache, connected to a system memory through a system bus, wherein the system memory stores all the image blocks of the frame, and the frame cache obtains a plurality of pixels of at least one image block of the frame from the system memory and stores the pixels; an observation model generator, connected to the frame cache, for reading the pixels of the at least one image block from the frame cache, and generating an observation model corresponding to the object and the read pixels according to the read pixels; and a particle filter controller, connected to the observation model generator, for obtaining the observation model from the observation model generator, and deciding and outputting an object tracking result of the object according to the observation model.