Solution cathode glow discharge atmosphere emission spectrometry (SCGD-AES) is affected by the matrix effect in aqueous solution. Moreover, actual water contains many elements and the components are relatively complex, which makes matrix effect more serious and leads to a decrease in accuracy of metal element concentration prediction. In order to reduce matrix effect of aqueous solution in SCGD-AES, quantitative analysis methods are often used to analyze metal elements. Among these methods, standard addition method is especially suitable for the situation that matrix effect or interfering substance is relatively significant. However, standard addition method is vulnerable to background interference, resulting in the error of results. Therefore, the background interference must be eliminated before standard addition method is carried out. The simplest method to eliminate the interference is off-peak correction method, which deduces the background intensity value measured at the left and right of the linear peak, so as to eliminate the background interference. Wavelet transform method is also applicable to eliminate background interference and it is universal. This method is applied to multi-scale stratification of wavelet, and then the low-frequency coefficient of wavelet is processed to obtain the corrected data. Here, Ca and Mg content in solution were predicted by off-peak correction and wavelet transform method based on standard addition method in a homemade SCGD- AES system. For the traditional standard addition method, the relative error of the Ca samples with concentrations of 5, 10 and 20 mg·L-1 were measured as 157.0%, 105.1% and 47.0%, respectively. The REs of Mg in the three groups of samples were 20.1%, 3.1% and 2.8%, respectively. However, when the standard addition method and off-peak correction were combined, REs of Ca were reduced to 15.4%, -8.8% and 3.3%, and REs of Mg were reduced to 14.5%, 0.1% and 0.8%, respectively. When standard addition method by wavelet transform to eliminate background interference was employed, REs of Ca decreased to 13.2%, -7.6% and -1.4% respectively, and REs of Mg decreased to 13.4%, -0.4% and 0.5% respectively. The experimental results show that the accuracy of Ca and Mg measurement is significantly improved by off-peak and wavelet transform method. The two methods can effectively eliminate background interference, reduce matrix effect and improve the prediction accuracy. The wavelet transform combined with standard addition method can be used for various background correction occasions, without selecting appropriate background correction points, and the prediction accuracy is higher, which has advantages compared with off-peak correction method.