The invention provides a nanocomposite material and a preparing method and application thereof. The method comprises the following steps of 1, preparing a multi-layer pore structure carbon nanomaterial modified by polydopamine; 2, distributing nano-metal particles on the modified material obtained in the step 1. According to the nanocomposite material and the preparing method and application thereof, the synthetized nanocomposite material can well fix lipase, thus triglyceride is directly detected, and in addition, according to a sensor prepared through the nanocomposite material, a screen-printed electrode is adopted, so that the nanocomposite material has a good industrialized application prospect. The nanocomposite material can well combine lipase, and the screen-printed electrode of which a work electrode is modified with the nanocomposite material shows good sensitivity, selectivity and capacity of resisting disturbance on the detection of triglyceride. Besides, the preparing process of the nanocomposite material is simple, and the screen-printed electrode has the advantages of being flexible, convenient to carry and the like; because of the disadvantages, a triglyceride sensing chip has a wide industrialized application prospect.