A picture encoding and decoding method, a picture encoding and decoding device and a network system are provided, in which, the picture encoding method includes: determining a prediction block used by a picture block according to a division manner of the picture block; determining a corresponding division level in the picture block or the prediction block of transform blocks corresponding to the picture block or the prediction block, in which, the transform blocks corresponding to the picture block or the prediction block include one or more transform blocks; determining a size of the transform blocks corresponding to the picture block or the prediction block according to the division manner of the picture block and the division level; determining identification information for identifying the division level corresponding to the transform blocks corresponding to the picture block or the prediction block; and writing the identification information into a code stream.