Single crystal diamond is a kind of crystal material with excellent performance, which has important application value in advanced scientific field. In the field of single crystal diamond growth by microwave plasma chemical vapor deposition (MPCVD), improvement of crystal growth rate is still a key challenge, although corrent high energy density plasma has been a ralatively effective method. In this work, a special plasma focusing structure was designed through magnetohydrodynamic (MHD) model simulation which then was used in the growth experiment based on the simulation. The plasma properties were studied by means of spectral analysis and plasma imaging, and late on single crystal diamond samples were synthesized. The simulation results show that the core electric field and electron density under focusing conditions were 2 times higher than those under normal conditions. The growth experiment results show that plasma with high energy density (793.7 W/cm³) is obtained under conventional microwave power (3500 W) and growth pressure (18 kPa), which is consistent with the model calculation results. We find that a certain amount of nitrogen instead of high energy density growth conditions can significantly change the growth morphology and affect the quality of the crystal. With those findings, we realize the growth rate of single crystal diamond up to 97.5 μm/h. Different from the way to obtain high energy density by increasing the growth pressure, single crystal diamond can be synthesized with high energy density under normal growth pressure and microwave power.