Tri-proof structure and mobile phone using the same

A mobile phone comprising:

• a first casing;
• a second casing made of soft material, the first casing being assembled to the second casing;
• a third casing assembled to the second casing;
• a first tri-proof structure for opposite left and right sides provided at opposite left and right sides of the mobile phone, the first tri-proof structure for the opposite left and right sides providing a protrusion at each of the opposite left and right sides of the first casing, providing a convex block at each of the opposite left and right sides of the third casing, and providing a first groove corresponding to each of the protrusions and a second groove corresponding to each of the convex blocks, the fits between the protrusions and the first grooves and the fits between the convex blocks and the second grooves each being interference fit;
• a second tri-proof structure for opposite upper and lower ends provided at the opposite upper and lower ends of the mobile phone, the second tri-proof structure for the opposite upper and lower ends providing a concavity at each of opposite upper and lower ends of the third casing, providing a strip structure assembled in each of the concavities at each of the opposite upper and lower ends of the second casing, and providing a protruding strip at each of the opposite upper and lower ends of the first casing, each of the protruding strips being assembled in one of the concavities and pressing one of the strip structures to form an interference fit;
• wherein the second casing further comprises a cosmetic surface at each of the opposite left and right sides of the mobile phone, the first casing and the third casing respectively further comprises an outer surface at each of the opposite left and right sides of the mobile phone, each of the cosmetic surfaces protrudes out of the corresponding outer surface of the first casing and the third casing.