Abstract: Abstract: The photosynthesis and growth of plants are affected by many environment factors such as temperature, humidity, light, carbon dioxide (CO2) concentration, electrical field and magnetic field. In this paper the effects of high voltage electricity on the photosynthesis of plants are studied experimentally. Two boxes A and B which have positive or negative high voltage electricity are used. Plants can be grown in the garden pot with electricity, and electrical sources are fixed inside the bottom of the boxes. On the top of box a LED (light-emitting diode) bulb is settled as photosynthesis light. We use red light in these experiments. Another box C with no electricity is used for contrast research. First, the static-electrical parameters such as capacitance and current of living tissue of pepper tree leaves are measured while the plants are cultivated with high static-electricity in the boxes. Experimental results show no matter which positive or negative electricity is added on the plants, the capacitances at different points of leaves are lowed by about 0.01 nF, and the currents at different points of plants increase by 1.00-2.00 μA. A high electrical field of several kilovolts per meter is created at the edges of leaves and branches while the plants are cultivated with high voltage electricity. In order to study how the photosynthesis of plants is affected by positive or negative electricity, the CO2 concentrations in the closed boxes A, B and C are measured during the same cultivation time, respectively. The results show that the CO2 concentration in the box B where plants are charged negatively decreases the most. In the experiment of green pineapple the decrease rate of CO2 concentration is 2 μL/(L·min) in A box, 2.35 μL/(L·min) in B box and 1.2 μL/(L·min) in C box. In the experiment of golden diamond tree the decrease rate of CO2 concentration is 0.3 μL/(L·min) in A box, 0.98 μL/(L·min) in B box and 0.12 μL/(L·min) in C box, respectively. In the experiments of pepper tree the decrease rate of CO2 concentration is 1.35, 1.50 and 1.02 μL/(L·min) in the boxes A, B and C respectively during the time from 10:50 to 11:30, and 0.88, 1.73 and 0.53 μL/(L·min) in the boxes A, B and C respectively during the period of 13:10-13:50. The measured results show the similar tendency of CO2 concentration decreasing and the photosynthesis of negatively charged plants is more improved. The photosynthesis of positively charged plants is also improved compared with the plants that are not charged. The chlorophyll fluorescence data of green pineapple are measured. The primary light energy conversion efficiency, yield and photochemical quenching parameter of green pineapple after cultivation with negative electricity are higher than those charged positively or not charged. This experimental study shows that negative high voltage electricity on plants increases the CO2 absorption rates of plants and promotes their photosynthesis greatly. In order to make clear the relationship between the electrical parameters of plants and the transmission of electrical signals in plants triggered by electrical stimuli, many experimental and theoretical works need to be carried out. How the electrical stimuli affect the photosynthesis and respiration of plants will be studied next.