The utility model relates to a measurement while-drilling instrument main valve cylinder with an anti-blocking function. According to the technical scheme, the measurement while-drilling instrument main valve cylinder with the anti-blocking function comprises a valve cylinder body, a sealing ring, a filter screen, a piston cap, small valve cylinder holes, a pressure bearing ring, a guiding shoe, a drive rod and a mushroom head. The pressure bearing head is arranged on the guiding shoe in a sleeved mode. The guiding shoe is in threaded connection with the valve cylinder body. The valve cylinder body is sleeved with the filter screen. The upper portion of the filter screen and the valve cylinder body are sealed through the sealing ring. The lower end of the filter screen is seated on in the pressure bearing ring to cover the multiple small valve cylinder holes in the lower portion of the valve cylinder body, so that large-particle solids in drilling fluid are prevented from entering the valve cylinder body through the small valve cylinder holes and making the piston cap get stuck. The piston cap is connected with the mushroom head through the drive rod. The measurement while-drilling instrument main valve cylinder with the anti-blocking function has the advantages that through additional arrangement of the filter screen, solid particles entering a driving assembly along with the drilling fluid can be greatly reduced, the probability that the driving assembly is blocked is lowered, the drilling fluid can still normally enter the main valve cylinder to balance internal pressure and external pressure of an instrument, and transmission of pulse signals of the drilling fluid cannot be affected; whether the measurement while-drilling instrument main valve cylinder is used in a large well or a small well, the measurement while-drilling instrument main valve cylinder will not influence normal use of the instrument.