The present invention discloses a method of mask reduction of low-temperature polysilicon thin film transistor array by use of photo-sensitive low-K dielectric, which comprises the steps of: defining a polysilicon-island on a preprocessed glass substrate; forming a gate oxide layer and a first metal layer in sequence; patterning the first metal layer to define a gate; forming a photosensitive dielectric layer; patterning the photosensitive dielectric layer and the gate oxide layer to form a plurality of contact holes; forming a transmissive pixel layer and patterning the same; and forming a reflective pixel electrode layer and patterning the same.