The invention provides a crack detection sensor based on a microstrip antenna and a detection method thereof. The invention is characterized in that the crack detection sensor comprises a dielectric substrate, one surface of the dielectric substrate is provided with a conductor patch through etching, deposition or corrosion, and the other surface of the dielectric substrate is adhered on a to-be-detected structure to form the complete sensor. According to the invention, a relationship between the length and the direction of a crack and resonant frequencies of radiation modes respectively parallel to the length direction and the width direction of the patch of the microstrip antenna can be established, and the length and the direction of the crack can be obtained based on the shifts of the resonant frequencies. The crack detection sensor based on the microstrip antenna provided by the invention has the advantages of a small size, light weight, low profile, capacity of being conformal to a carrier, simple manufacturing, low cost, etc.; moreover, the crack detection sensor employs microwave detection technology, which facilitates wireless detection and signal processing.