Objectives: To obtain the positions, velocities, and acceleration of actuators of the 4-DOF of the parallel gripper, and optimization of the mechanism is carried out to find the optimal dimensions of the mechanism. Methods: Kinematic analysis is carried out to find the positions and velocities of the gripper of the mechanism. The method used to solve the position of the mechanism is inverse kinematics. A source code is written in MATLAB software to find the positions and velocities of the gripper. This software is a computing platform which can solve large size matrices easily which is most suitable for robots. A model of the mechanism is created in CATIA with constraints. The developed CATIA model is used in ANSYS software for structural analysis. The method used for finding optimal dimensions is Genetic algorithms. Optimization is carried out using Genetic Algorithms (GA’s) using the Energy Manipulation Index as an objective for obtaining the optimal dimensions of the parallel gripper mechanism. Finally, ADAMs software is used to simulate the mechanism. Findings: using inverse kinematic equations the results of displacements, velocities, and accelerations obtained for in-plane horizontal motion, and in-plane vertical motion s plotted. After checking the gripper performance, It is observed that the in-plane vertical transmission is better than the in-plane horizontal transmission. Based on the Energy Manipulation Index (EMI), the performance-to-effort ratio of the gripper object is calculated. It tells about the physical significance of energy transfer efficiency. If the energy occupied by the end-effector is higher than the 4-DOF Parallel Gripper achieves higher efficiency and possesses better manipulability performance. Maximum EMI is taken as an objective for optimization using GA. Simulation is carried out using ADAMS software to determine the driving forces or torques. Novelty/improvement: In this paper the performance index EMI is taken as objective to find the optimal dimensions of the 4-DOF of parallel gripper. Keywords: DOF parallel gripper, Inhand manipulation, Inhand twisting, Driving force, Energy Manipulation Index (EMI)