A thin film solar cell comprises a base and a plurality of cell units provided at the base. Each cell unit comprises a back contact layer, a light-absorbing layer, a buffer layer and a front contact layer which are sequentially arranged. A first recess is arranged between and extending through the back contact layers of any two adjacent cell units. An insulation portion is filled in the first recess. Each cell unit has a second recess extending through the light-absorbing layer and the buffer layer. The front contact layer of each cell unit extends into its second recess to contact the back contact layer of the cell unit adjacent thereto. A third recess is formed between the two adjacent cell units, such that the front contact layers of the two adjacent cell units are spaced apart and insulated from each other.