The invention discloses a fast connecting joint of a downhole measuring while-drilling instrument. The fast connecting joint comprises a male joint
assembly and a female joint
assembly which are mutually connected; the female joint
assembly comprises a central extended
pipe, a female
drill collar nipple, an electrical appliance converter base, an electrical appliance converter I and a lower centralizing seat; the male joint assembly comprises an electrical appliance converter II, a male
drill collar nipple, an extended central
pipe, a middle connecting joint, a middle centralizing seat, a threaded sleeve, a lock ring, an electrical appliance connector, a main body central
pipe and a main body electrical appliance pipe; and the female
drill collar nipple and the male drill collar nipple areconnected together, the electrical appliance converter II sleeves the electrical appliance converter I, and the lower centralizing seat sleeves the extended central pipe. Through the fast connectingjoint, the means of fast, simple, convenient and reliable connecting between a measuring while-drilling tool and the measuring while-drilling instrument is realized, automatic and fast connecting andsealing in the screw connection process of the measuring while-drilling measuring tool and the measuring while-drilling instrument can be realized, and the fast connecting joint is simple, convenientand practical in structure, and low in cost.