The non critical phase matching KTP optical parametric oscillator (OPO), pumped by dual cell stimulated Brillouin scattering (SBS) pulse width tunable laser system, has achieved tunable pulse width and comparatively high transforming efficiency with low power pumping laser of ranging from less than 1 ns to 6 ns. The output character of this OPO is also analyzed along with experiment results according to characteristics of long pulse pumped OPO.