The promising development of minimally invasive laser surgery for the treatment of hemorrhoids is associated with a combination of diagnosis and treatment in time and space. The purpose of this study was to develop the structure of such a device allowing performing minimally invasive hemorrhoids treatment with laser coagulation under interstitial ultrasound visualization in real time. The medical complex includes a diagnostic unit, a laser unit and a control system. In turn, the diagnostics module, which allows real-time monitoring, includes a Doppler sensor for performing blood vessel search and measuring blood flow velocity, an ultrasonic sensor for visualization of soft tissues, and monitoring of the laser vascular coagulation operation. The laser unit consists of a laser emitter; a fiber-optic instrument serving to deliver laser radiation to the impact zone; the power and cooling system necessary to maintain the operating temperature of the laser. To carry out numerical calculations of laser radiation parameters, a mathematical model was developed. For its implementation, a computer program was developed that allows a numerical evaluation of the effects of laser vascular coagulation. The given program allows to estimate the influence of laser radiation on blood vessels and perivenous tissue and to analyze the degree of denaturation of tissue molecules. For calculations, optical and thermodynamic parameters of biological tissues are used, which ensure a satisfactory match of the simulation results with known literary data.