Objective: To study the effects of titania nanotubes with three different diameters on human gingival fibroblast (HGF). Methods: Three groups of specimens were prepared. Titania nanotubes with diameters of 30, 100, and 200 nm were synthesized on titanium surfaces through electrochemical anodization at 10, 30, and 60 V, respectively. Specimens were assigned into the three groups according to the diameter of the titania nanotubes. Pure smooth titanium without any treatment was set as the control group. HGF were seeded on the surface of the samples. The cell morphology on the specimens was observed with immunofluorescence staining after 2 h, the cell adhesion after 2 d and cell proliferation after 1, 3, and 7 d were detected using methyl thiazolyl tetrazolium assay, and the secretion of type Ⅰ collagen after 7 d was determined using enzyme-linked immunosorbent assay (each group has three samples for each experiment). Results: HGF on the control group exhibited an oval shape without noticeable extensions. HGF on titania nanotubes with a diameter of 30 nm and titania nanotubes with a diameter of 100 nm elongated further and were arranged orderly. HGF on titania nanotubes with a diameter of 200 nm were sparsely distributed without noticeable extensions. Titania nanotubes with a diameter of 30 nm and titania nanotubes with a diameter of 100 nm could enhance the cell attachment (0.603±0.021 and 0.773±0.045), and secretion of type Ⅰ collagen [(36.5±9.5) and (47.7±4.5) µg/ml, respectively] compared with the control group whose cell attactment was 0.427±0.057, and secretion of type Ⅰ collagen was (22.2±5.9) µg/ml (P<0.05). Furthermore, titania nanotubes with a diameter of 100 nm showed more cell attchment than titania nanotubes with a diameter of 30 nm did (P<0.05). Ttania nanotubes with a diameter of 200 nm clearly impaired the cell adhesion (0.250±0.046) and secretion of type Ⅰ collagen [(10.1±3.7) µg/ml] compared with the control group (P<0.05). At each time point, titania nanotubes with a diameter of 100 nm showed the highest cell proliferation, and the amount of cell proliferation was significantly higher than that on the titania nanotubes with a diameter of 200 nm and the control group at each time point (P<0.05), and was also significantly higher than that on the titania nanotubes with a diameter of 30 nm at day three (P<0.05). At each time point, titania nanotubes with a diameter of 200 nm showed the lowest cell proliferation, which was significantly lower than that on the control group at each time point (P<0.05), except that there was no significant difference in the amount of cell proliferation between titania nanotubes with a diameter of 200 nm and the control group at day one (P>0.05). Conclusions: Titania nanotubes with a diameter of 100 nm can improve the HGF attachment, proliferation, and secretion of type Ⅰ collagen.