This study is a randomized, double-blinded, placebo-controlled phase 2 clinical trial to evaluate the immunogenicity and safety of Inactivated Rotavirus Vaccine (IRV) in children (aged 2-71 months). Primary immunogenicity endpoints in two age groups are the anti-RV neutralizing antibody geometric mean titers (GMTs) 28 days after the final dose, anti-RV neutralizing antibody geometric mean increase (GMI), and seroconversion rates between baseline and 28 days after the final dose. The secondary safety endpoints are the number of adverse events/reactions within 30 minutes after each dose, the number of solicited adverse events/reactions within 7 days after each dose, the number of unsolicited adverse events/reactions within 28/30 days after each dose, and the number of serious adverse events (SAE) between the first dose up to 6 months after the final dose. The exploratory endpoints are the anti-RV IgG and IgA antibody GMT 28 days after the final dose, GMI and seroconversion rates of anti-RV IgG and IgA antibody between baseline and 28 days after the final dose, GMT and seropositive rates of anti-RV neutralizing antibody, IgG antibody and IgA antibody 90, 180, and 360 days after the final dose. Besides, as the exploratory endpoint, the GMT, GMI, and seroconversion rates of cross-neutralizing antibodies against G3 and G9 type of RV, gene transcription differences in peripheral blood mononuclear cells on Day 0 and 28 after the final dose will be assessed.