The invention discloses a photonic crystal nano-fluid sensor based on nano-replication and a preparation method thereof. The p photonic crystal nano-fluid sensor comprises a photonic crystal structure and an optical transparent covering layer. The photonic crystal structure comprises a glass substrate, a low refractive index grating layer formed by UV solidified substances, and a high refractive index material layer deposited on the grating layer. The preparation method comprises steps that a quartz grating master template having a grating period structure is prepared; the UV solidified substances are coated on a glass slide in a spun manner; the quartz grating master template is heated, and stripping glue is dropped in a grating groove, and then the glass slide is disposed on the quartz grating master template in a covered manner, and is solidified; a cover glass is attached to the back surface of the glass slide; the high refractive index material is deposited on the grating layer to acquire the high refractive index material layer; the optical transparent covering layer is attached to the surface of the material layer, and then the optical transparent covering layer and the material layer are bonded together, and in addition, a nano-fluid channel is formed between the optical transparent covering layer and the grating groove. The photonic crystal nano-fluid sensor has advantages of concise and fast preparation, high production precision, low costs, and applicability in batch production.