1. A method of positron emission tomography (PET) imaging; wherein the method is performed by an equipment and the equipment comprises a computer imaging system, a device carrying a detected object and a detector system disposed around the detected object for collecting gamma photons emitted in a positron annihilation event; wherein a multi-pinhole plate is disposed between the detected object and a detector, and the detected object is traced by a radioactive isotope of β+ decay; wherein the multi-pinhole plate is configured to collimate gamma photons, which allows an image to be acquired by detecting individual gamma photons emitted from annihilations without requirement to detect another photon coincident in time via a time coupling electronic circuit; the imaging method comprising the following steps: step 1), collecting, by the detector, gamma photon projections from a plurality of angles through the multi-pinhole plate, for generating a projection image which is denoted by p(x, y), wherein the x and y denote a coordinate of two dimensions of the detector, and a value of p represents photon counts detected by that detector individually without coincidence via the time coupling electronic circuit; and step 2), reconstructing, by the computer imaging system, a three-dimensional image based on all the projection images.