The invention discloses an in-situ measuring device for anti-liquefaction capability of an offshore seabed sediment; the in-situ measuring device comprises a probe, a balance weight bin and a data module, the probe penetrates into the seabed sediment by a free falling body effect, the balance weight bin is installed at the upper end of the probe, a balance weight block is placed in the balance weight bin, a depth measuring component is installed outside the probe, a one-way moving mechanism is arranged between the depth measuring component and the probe, the one-way moving mechanism can move the depth measuring component upward when the probe penetrates into the seabed sediment, and can keep the depth measuring component in the last position of the upward movement when the probe is taken out from the seabed sediment so as to the depth of in-penetration of the probe into the seabed sediment; the data module comprises an acceleration measuring component and a power supply module, and thepower supply module supplies power to the acceleration measuring component. The in-situ measuring device combines the advantages of SPT, CPT and other in-situ measurement methods, has the advantagesof simple operation and high precision, and the like, and provides accurate measurement data and a research basis for prevention and treatment of coastal geological disasters.