In order to measure the correlation propeties of two Boolean functions,the global avalanche characteristics of Boolean functions constructed by concatenation are discussed,i.e.,f_1‖f_2and f_1‖f_2‖f_3‖f_4.Firstly,for the function f = f_1‖f_2,the cross-correlation function of f_1,f_2 in the special condition are studied.In this case,f,f_1,f_2 must be in desired form.By computing their sum-of-squares indicators,the crosscorrelation function between f_1,f_2 is obtained.Secondly,for the function g = f_1‖f_2‖f_3‖f_4,by analyzing the relation among their auto-correlation functions,their sum-of-squares indicators are investigated.Based on them,the sum-of-squares indicators of functions obtained by Canteaut et al.are investigated.The results show that the correlation property of g is good when the correlation properties of Boolean functions f_1,f_2,f_3,f_4 are good. In order to measure the correlation propeties of two Boolean functions, the global avalanche characteristics of Boolean functions constructed by concatenation are discussed, ie, f_1∥f_2and f_1∥f_2∥f_3∥f_4.Firstly, for the function f = f_1∥f_2, the The cross-correlation function of f_1, f_2 in the special conditions are studied.In this case, f, f_1, f_2 must be in the desired form.By computing their sum-of-squares indicators, the crosscorrelation function between f_1, f_2 is obtained. Secondly, for the function g = f_1∥f_2∥f_3∥f_4, by analyzing the relation among their auto-correlation functions, their sum-of-squares indicators are investigated.Based on them, the sum-of-squares indicators of functions obtained by Canteaut et al.are investigated. The results show that the correlation property of g is good when the correlation properties of Boolean functions f_1, f_2, f_3, f_4 are good.