The present disclosure discloses an in situ UPb dating method for calcite, including: cutting a calcite sample to prepare an epoxy resin sample target; placing the sample in a laser ablation sample chamber, and adjusting a position of the sample in an optical axis direction; conducting line scanning ablation on the sample target, and measuring ion signal intensity data of .sup.43Ca, .sup.88Sr, .sup.139La, and .sup.238U; conducting two-dimensional (2D) element imaging to obtain a 2D element content distribution map; according to the 2D element content distribution map, determining a high-U analysis target area, conducting point ablation on the high-U target area, and measuring ion signal intensity data of .sup.206Pb, .sup.207Pb, and .sup.238U; and after the element signal data is obtained, calculating .sup.207Pb/.sup.206Pb and .sup.238U/.sup.206Pb fractionation coefficients, correcting ratios of an unknown sample, constructing a Tera-Wasserbug diagram, and calculating age data and an initial Pb isotope (.sup.207Pb/.sup.206Pb) composition of the calcite sample.