The invention discloses a driven mechanical arm used for a laser excision minimally invasive surgery. The driven mechanical arm comprises a foundation bed, a machine body, rotary connecting rods and an end effector. The driven mechanical arm has four rotary degrees of freedom, wherein the first degree of freedom is used for the integral rotation of the machine body; the second degree of freedom adopts the parallel connecting rods to enable the end effector to realize telecentric movement around a fixed point, and the first two degrees of freedom control the integral direction of the end effector; the third degree of freedom realizes the feed movement of the end effector along the axial line of a human body entry point; the fourth degree of freedom realizes the rotation movement of the end effector along the axial line of the human body entry point; and last two degrees of freedom specifically control the direction and the position of the laser area of the end effector. By use of the driven mechanical arm, surgery requirements can be subjected to complete mechanical spacing, four motors can pass through a telecentric point no matter how to rotate, in addition, movement and resolving are mutually independent, and control is simple. The driven mechanical arm has the advantages of simple mechanism and low processing cost, and can effectively lower the difficulty and the cost of a benign prostatic hyperplasia laser excision minimally invasive surgery.