The equation parser-calculator for COMPLEX number math expressions with parse-tree builder and user-friendly interface for parsing and calculation a run-time defined math complex expression. The math expressions is represented as string in a function style F(x1, x2,..., xn) =f(x1, x2,..., xn) , where F(x1, x2,..., xn) - declares number and names of the variables; f(x1, x2,..., xn) - math expression may contain: variables x1, x2,..., xn and constants, which can be complex numbers (for designation image part of the complex numbers use 'i' or 'j' letter), operators: + - * / ^ @, functions abs, arg, conj, cos, cosh, exp, imag, log, log10, norm, real, sin, sinh, sqrt, tan, tanh, constants e= 2.71828182845904 and pi= 3.14159265358979, and user defined functions and constants. For example: F(x, y) = 3i*x^2+y^2j+e/4i, F(x1, x2, y) = (x1-sin(x2@y))/y, F()=5+6i+pi.