The time-like minimal surface in Minkowski space time is an interesting model in Lorentzian Geometry and field theory. The Euler-Lagrange equation derived from the area functional turns out to be a quasilinear wave equation, for which the investigation of its Cauchy problem is challenging, especially for low regularity initial data. We study the radially symmetrical equation in the (1+3)-dimensional Minkowski space time, and expect to prove it’s globally well-posed at the critical Sobolev regularity.