In this paper solution of mixed complex boundary value problem of first order is considered. The basic term in the problem with respect to space variables, has Cauchy-Riemann operator. We first use Laplace transformation to introduce spectral problem. Then we investigate for corresponding Fredholm's type. The spectral problem here is different from classical boundary value problems. Here boundary conditions are nonlocal and global and in general linear.At the end we find asymptotic expansionfor the solution of spectral problemwhich depends on unknown complex parameter. With the help of this asymptotic expansion we prove existence and uniqueness of mixed problem.