A coincidence technique-based X-ray detection device and composition analysis method are provided, wherein the X-ray detection device includes: a sample holding device; an excitation unit for outputting X-rays with continuously adjustable energy; detectors comprising two SiC semiconductor detectors and two SiPIN semiconductor detectors; a signal processing unit for performing amplification, analog-to-digital conversion and classification on the detected signals to obtain energy information; a data processing device connected to the signal processing unit and used for analysis and calculation according to the energy information and determining element type and content of the sample to be tested, wherein the data processing device comprises a processor and a memory, the processor is used for executing following program modules stored in the memory: a storage module, a baseline recovery module, a calibration curve construction module, an extraction module, an effective energy information determination module, and a peak comparison module.