Abstract: Through designing a bypass-door system for a supersonic aircraft, which implemented adjustment in conformity to the control curves of the two-variable function （Fig. 1 ）, a method for engineering realization of some separable mul-tivariable functions has been put forward, It means, for any control function of n variables f （x1,x2,…,xn）, ifthe function, called separable by the author, can be divided into subfunction of each single variable, then the sum of these subfunctions is just equal to the original function, i. e.f（x1,x2,…,xn）=f1（x1）+f2（x2）+…+fn（xn）.A practical bridge circuit with parameters realizing the control curves for the bypass-door has been designed （see Fig. 4）.Moreover, the simple method of changing the characteristics of the control curves by adjusting resistors on the bridge arms has been adopted according to the test flight requirements of the system, and an actual numerical example has been given.The above mentioned engineering realization and adjustment method for the two-variable function have done their bit for the research on the simulator reproducing the function of more than two variables and may be also valuable for design of the system with multiple input but single out-put.