An inverted-embedded optical tweezers system combining a micropump was assembled. The escaping velocities and acting forces of particles and hemocytes could be measured. After experiments and calculations, the escaping velocity of a 6 mum bead was 0.20 mum/s and the trapping force was 0.012 pN when the power was 5 mW. The escaping velocity of a granulocyte was 0.80 mum/s and the trapping force was 0.077 pN when the power was 60 mW. The escaping velocity of the blood cancer cell (K562) was 1.13 mum/s and the trapping force was 0.13 pN when the power was 30 mW. The escaping velocity of a red blood cell was 0.67 mum/s and the trapping force was 0.051 pN when the power was 60 mW. Considering the effect of the wall and the beads' sizes, one could modify the trapping force. The trapping force of 6 mum bead after modification was larger 1.3% than that before modification. The trapping force of 12.32 mum bead after modification was larger 3.5 % than that before modification. The distances between the beads and the wall actually affect the trapping force, but the differences were lower than 4 % in this research.