Low density gas conical implosion can produce high density plasmas with a volume compression ratio of 106 to 109, and a temperature over 10 eV. As the temperature is limited by the plasma-wall interaction, to further increase the density and temperature and confine the plasma energy, we use a theta pinch at the top of the imploding cone. A conical magnetohydrodynamic simulation method is used to calculate the properties of the plasma, in which three cases, i.e., pure conical fluid compression, pure theta pinch, and synergic compression of fluid compressing and theta pinch, are calculated in a two-dimensional conical geometry. Simulation shows that synergic compression can improve the energy confinement and efficiently raise the temperature of the plasma. Different parameter combinations are calculated to find the optimum performance.