In recognition of the lack of solar radiation (Rs) monitoring data at some meteorological stations, FAO56 recommends the Ångström–Prescott (A–P) equation for estimating Rs and gives recommended coefficient values (recommended values), which are widely used in the estimation of the reference crop evapotranspiration (ETo). Compared with the corrected coefficient values (corrected values), the temporal and spatial distribution characteristics of the average relative errors (MRE) of Rs and ETo in China caused by the recommended values are studied. The MRE of the estimated annual Rs and ETo all tend to increase from the northwest inland to the southeast coast. However, the monthly Rs and the monthly ETo have an MRE that presents a double-valley curve and a unimodal curve, respectively, of the year, leading to inconsistency between the inter-monthly spatial distribution of the MRE of the monthly Rs and the monthly ETo. The recommended values have considerable influence on the daily Rs in the year and the daily ETo during the critical crop growth period (April–September). Therefore, the suitability of the recommended values should be scrutinized by taking into account the influence on Rs and ETo at different temporal and spatial scales. For the lack of Rs monitoring data in China, this paper can support whether the recommended values can be used in estimating Rs and ETo by using A-P equation and its error.