Abstract: Compared with the traditional cylindrical fuel rod, petal-shape fuel rod has higher security, so it is of great significance to study thermal-hydraulic characteristics of petal-shape fuel rod utilized in the pressurized water reactor. In this paper, the 5×5 petal-shape fuel rod bundle assembly was numerically simulated by STAR-CCM+. The sensitivity of turbulence model was analyzed. In this study, the relative errors between the SST k-ω model and the experimental data were within 5%, so the SST k-ω model was selected herein. According to AP1000 PWR, boundary conditions were set as the outer wall with adiabatic non-slip wall, and the reference pressure of fluid domain, inlet velocity, inlet temperature and the outlet pressure were set as 15.5 MPa, 1.25-3 m/s, 565.55 K and 0 MPa, respectively. The heating mode of solid domain was set as uniform heating, and the volumetric heat release rate was set as 1.17 times that of AP1000 PWR. The interface between fluid domain and solid domain was connected by INTERFACE. Five different inlet velocities (v_in=1.25 m/s, 1.5 m/s, 2 m/s, 2.5 m/s, 3 m/s) and four different spiral pitches (H=250 mm, 500 mm, 750 mm, 1 000 mm) were selected. The key thermal-hydraulic parameters such as secondary flow velocity, temperature and heat transfer coefficient were calculated and analyzed. The influence of inlet velocity and spiral pitch on flow and heat transfer characteristics of the assembly was obtained. The results show that the spiral of petal-shape fuel rod can enhance the lateral flow of the coolant, so the secondary flow velocity near the fuel rod wall is related to the structure of fuel rod, and compared to the outer convex arc region, it is higher in the inner concave arc region. And also, it is very low in the central area of the subchannel because it is far away from the fuel rod wall. Besides, the surface temperature distribution of the fuel rod at the same height is periodic. The heat transfer coefficient firstly decreases along the flow direction, and then gradually stabilizes. And as inlet velocity increases, the mixing in the rod bundle is gradually enhanced, the non-uniformity of temperature distribution on the fuel rod surface is gradually reduced, and the heat transfer coefficient is increased. The heat transfer coefficient along the fuel rod bundle decreases with the increasing pitch. When the pitch is larger than 750 mm, the heat transfer coefficient of fuel rod is the same as that of non-twisted one, or even lower.