We report a new high-sensitivity H i mapping observation of the NGC 5055 galaxy group over an area of with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Our observation reveals that the warped H i disk of NGC 5055 is more extended than what was previously observed by WSRT, out to   (61.7 kpc). The total H i mass of NGC 5055 is determined to be ∼1.1 × 1010M⊙. We identified three H i clouds with H i masses of the order of ∼107M⊙ at the southeastern edge of the H i disk, as well as a candidate high-velocity cloud with an H i mass of (1.2 ± 0.5) × 106M⊙ to the north of NGC 5055. The H i content of UGCA 337 is robustly detected for the first time by the FAST observations. It has a narrow H i linewidth of W50 = 17.4 ± 3.8 km s−1 with a total H i mass of (3.5 ± 0.3) × 106M⊙. Comparing the gas content and g−r color of UGCA 337 with typical low-mass dwarf galaxies, UGCA 337 appears relatively gas-poor despite its blue color. This suggests that UGCA 337 may have undergone gas stripping in the past. We also analyzed the possible origin of the diffuse H i clouds located at the outskirts of NGC 5055, and speculate that they might be the remnant features of a merger event in the past.

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