U–Pb geochronology of carbonate by laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) is a rapidly growing research field due to its great potential to solve geological problems related to basin, tectonic, magmatism, and environmental evolution. In this paper, grid diagram was used to improve analytical efficiency. Two analytical modes of mixed collectors and multiple ion counting collectors were used on a Thermo Fisher Neptune Plus for carbonate U–Pb dating. Jet sample cone and X skimmer cone with Ar-N2 plasma (small addition of nitrogen into the sample gas flow) was used to enhance signal sensitivity of U and Pb. Our results showed that the sensitivity with Jet + X cones and adding nitrogen was a factor of two and eight greater than using standard sample cone and H skimmer cone in Ar-N2 plasma and Ar plasma, respectively. The fluence, repetition rate and spot size of the laser were investigated to assess effects on U–Pb results of different laser parameters. Medium energy fluences (~6 J/cm2) and medium ablation frequency (6 or 8 Hz) are suitable laser parameters for most samples to gain good U–Pb dating results for carbonate. Our new technique was evaluated by investigating five carbonate standards with U–Pb ages ranging from 2.4 to 254 Ma, in good agreement with their reference values. Our improved method was successfully applicable to date carbonate concretion, hydrothermal calcite vein, and peperite, which yielded new age results coinciding with stratigraphic relationship, structure analysis, and other dating methods.