In this paper, the electronic and piezoelectric properties of two-dimensional Janus CrXY (X/Y=S, Se,Te) systems were investigated. The results show that the Janus CrXY systems are excellent semiconductor materials and the band gap widths of Janus CrXY range from 0.27 eV to 0.83 eV. The strain regulation in the x-axis direction has a great influence on the band gap, while the strain regulation in the z-axis direction has little influence on the band gap, indicating that the electronic properties of the system have good stability in the z-axis direction. The piezoelectric properties of the system were studied by density generalized perturbation method, the results show that all three materials have large out-of-plane piezoelectric coefficients d33, especially, the d33 of CrSeTe reaches 56.89 pm/V, which is about ten times that of the common piezoelectric material AlN (d33=5.60 pm/V). This research provides theoretical support for the practical application of two-dimensional Janus CrXY systems in the field of flexible and intelligent nanomaterials.