This study proposes a thin-film solar cell composed of periodic plasmonic titanium nanoparticles (Ti NPs) and indium phosphide (InP) thin films. By adjusting the size and position of plasma Ti NPs and combining with the transparent conductive layer ITO and anti-reflection layer SiO2, the parameters of InP thin film solar cells can be improved. The experimental results show that the average absorption rate reaches 96% in the wavelength range of 350-850 nm. The absorption rate reached 99.9% in multiple wavelength ranges. This study has successfully increased the short circuit current to 31.996mA/cm^2, power conversion efficiency (PCE) to 29.634% and open circuit voltage to 1.053V of InP thin film solar cells.