According to the geomagnetic 3 component absolute survey data of China for 1950 similar to 1990, and using the method of spherical cap harmonic analysis, this study calculates the spherical cap harmonic(SCH) models of the geomagnetic residual field in China for 1950 similar to 1990 and draws corresponding residual maps. The root mean square (RMS) deviations of SCH models of geomagnetic residual field are 93. InT(1950), 128.9nT (1960), 107.2nT( 1970). 107.6nT( 1980) and 95.2nT(1990) for DeltaX, 74.8nT( 1950), 98. 1nT( 1960), 89.2nT(1970), 89.9nT(1980) and 84.0nT(1990) for DeltaY, 122.2nT(1950), 135.0nT(1960), 137.7nT ( 1970), 110. InT(1980) and 107.5nT(1990) for DeltaZ, respectively. Based on the SCH models of the geomagnetic residual field in China and the DGRF models of the global geomagnetic field, the SCH models of the geornagnetic field in China for 1950 similar to 1990 are given, and corresponding geomagnetic maps are drawn, too. The pole of the spherical cap is at 36degreesN and 104degreesE, and its half angle is 30degrees, and the truncation order of the spherical cap harmonic models is 8. The boundary effect of SCH model is analysed and discussed.
