[Objective] Fluoride (F-) is ubiquitous in groundwater and it is listed as Class III specific carcinogen by International Agency for Research on Cancer. Presently, Huaihe River Basin is identified as a region with F- rich groundwater in China. In order to comprehensively evaluate groundwater F- exposure risk in this basin, this study is to assess its risk magnitude of investigating wells and to predict its risk probability in at unmonitored points based on the recently obtained high-density hydrochemical data. [Methods] This study is to assess the risk magnitude and likelihood for F- rich groundwater in Huaihe River Plain, China using Risk Magnitude and Indicator Kriging methods, and discusses how it formed additionally. [Results] The results show F- concentrations from 5575 investigating wells are in the range of 0.01~5.45 mg/L, with a median of 1.02 mg/L and a mean of 1.97 mg/L, respectively. F concentrations in plain areas are significantly higher than those in hilly areas. There are 548 (9.83%) wells with High Risk Magnitude, and 576 (10.33%) wells with Very High Risk Magnitude, which are predominant positioned in inland plain. Compared with deep groundwater, shallow groundwater exhibits higher F- levels and spatial variability. Based on the prediction of shallow and deep Risk Probability maps, the potential high F- hazard areas over shallow groundwater encompass more than 5137 km2, while the counterpart over deep groundwater is 864 km2; where 3.14 million people are estimated to be potentially exposed to F- contamination. The Risk Probability map of shallow groundwater shows a similar spatial pattern with that of deep groundwater, and both Risk Probability peaks are located in inland plain areas. [Conclusions] It is the main route for inhabitants exposed to F- through drinking groundwater. The spatial coincidence of high F- Risk Probability and high incidence rate of fluorosis observed in inland plain, which might suggest that groundwater F- level is related to the fluorosis cluster. F- rich groundwater is of in-situ origin, and F- is manly derived and released on fluorite dissolution. Besides, alkaline desorption and evaporation concentration affect the formation of high F- groundwater. This paper carried out research on exposure risk of F- rich groundwater from Huaihe River Plain, China, which results can provide scientific basis for the rational utilization and management of regional groundwater.