With increasing demand for energy, broaden renewable energy of income and reduce expenditure is becoming more and more important. Diffuse radiation (Rd) is an important consideration in building energy saving. Hundreds of methods were developed to calculate Rd because it is seldom available in many countries and its spatial-pattern is strongly station-dependent. There are only 13 stations that monitor both global solar radiation (Rs) and Rd after 1993 across China. Based on 812640 measurements of daily Rs and Rd collected from 80 stations across China during 1957–2014, we wished to calibrate and validate a simple approach, which can be easily used to predict Rd over both daily and monthly periods for all locations in China and gave the accurate values of parameters. The approach, of the case study method, is based on Rs and extra-terrestrial solar radiance (Ra). Results showed that the daily method can be employed well, while the monthly approach was applied well in the Southern Region (SR) only. The monthly approach of the Northern Region (NR) was improved using its regional characteristics. The methods achieved can effectively estimate Rd and strongly apply in engineering for only two parameters, which accurate values for all stations has been offered.